Electroactive polymer devices for controlling fluid flow

ABSTRACT

The invention describes devices for controlling fluid flow, such as valves. The devices may include one or more electroactive polymer transducers with an electroactive polymer that deflects in response to an application of an electric field. The electroactive polymer may be in contact with a fluid where the deflection of the electroactive polymer may be used to change a characteristic of the fluid. Some of the characteristic of the fluid that may be changed include but are not limited to 1) a flow rate, 2) a flow direction, 3) a flow vorticity, 4) a flow momentum, 5) a flow mixing rate, 6) a flow turbulence rate, 7) a flow energy, 8) a flow thermodynamic property. The electroactive polymer may be a portion of a surface of a structure that is immersed in an external fluid flow, such as the surface of an airplane wing or the electroactive polymer may be a portion of a surface of a structure used in an internal flow, such as a bounding surface of a fluid conduit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/383,005, filed Mar. 5, 2003 and entitled, “Electroactive PolymerDevices for Controlling Fluid Flow”; the 10/383,005 application claimspriority under 35 U.S.C. §119(e) from U.S. Provisional PatentApplication No. 60/362,560, filed on Mar. 5, 2002; and the 10/383,005application is also a continuation-in-part and claims priority from U.S.patent application Ser. No. 09/792,431, filed Feb. 23, 2001, issued asU.S. Pat. No. 6,628,040 on Sep. 30, 2003, which claims priority under 35U.S.C. §119(e) from a) U.S. Provisional Patent Application No.60/184,217 filed Feb. 23, 2000, and b) U.S. Provisional PatentApplication No. 60/190,713, filed Mar. 17, 2000; and the 10/383,005application is a continuation-in-part and claims priority from U.S.patent application Ser. No. 10/154,449, filed May 21, 2002, issued asU.S. Pat. No. 6,891,317 on May 10, 2005, which claims priority under 35U.S.C. §119(e) from U.S. Provisional Patent Application No. 60/293,003,filed on May 22, 2001; and the 10/383,005 application is acontinuation-in-part and claims priority from U.S. patent applicationSer. No. 10/053,511, filed Jan. 16, 2002, issued as U.S. Pat. No.6,882,086 on Apr. 19, 2005, which claims priority under 35 U.S.C.§119(e) from a) U.S. Provisional Patent Application No. 60/293,005 filedMay 22, 2001, and b) U.S. Provisional Patent Application No. 60/327,846,filed Oct. 5, 2001; and the 10/383,005 application is also acontinuation-in-part and claims priority from U.S. patent applicationSer. No. 09/619,847, filed Jul. 20, 2000, issued as U.S. Pat. No.6,812,624 on Feb. 27, 2007, which claims priority under 35 U.S.C.§119(e) from a) U.S. Provisional Patent Application No. 60/144,556 filedJul. 20, 1999, b) U.S. Provisional Patent Application No. 60/153,329filed Sep. 10, 1999, c) U.S. Provisional Patent Application No.60/161,325 filed Oct. 25, 1999, d) U.S. Provisional Patent ApplicationNo. 60/181,404 filed Feb. 9, 2000, e) U.S. Provisional PatentApplication No. 60/187,809 filed Mar. 8, 2000, f) U.S. ProvisionalPatent Application No. 60/192,237 filed Mar. 27, 2000, g) U.S.Provisional Patent Application No. 60/184,217 filed Feb. 23, 2000; andthe 10/383,005 application is a continuation-in-part and claims priorityfrom U.S. patent application Ser. No. 10/007,705 filed on Dec. 6, 2001,issued as U.S. Pat. No. 6,809,462 on Oct. 26, 2004, which claimspriority under 35 U.S.C. §119(e) from U.S. Provisional PatentApplication No. 60/293,004 filed May 22, 2001, and which is also acontinuation in part of U.S. patent application Ser. No. 09/828,496,filed on Apr. 4, 2004, Issued as U.S. Pat. No. 6,586,859 on Jul. 1,2003, which claims priority from U.S. Provisional Application No.60/194,817 filed Apr. 5, 2000; and the 10/383,005 application is acontinuation-in-part and claims priority from co-pending U.S. patentapplication Ser. No. 10/066,407, filed on Jan. 31, 2002 and issued asU.S. Pat. No. 7,052,594 on May 30, 2006; each of the patent applicationslisted above is incorporated by reference herein in its entirety for allpurposes.

U.S. GOVERNMENT RIGHTS

This application was made in part with government support under contractnumber N00014-00-C-0497 awarded by the Office of Naval Research. Thegovernment has certain rights in the invention.

BACKGROUND OF THE INVENTION

The present invention relates generally to electroactive polymer devicesthat convert between electrical energy and mechanical energy. Moreparticularly, the present invention relates to fluidic communicationcontrol devices and systems comprising one or more electroactive polymertransducers.

Fluid systems are ubiquitous. The automotive industry, the plumbingindustry, chemical processing industry and the aerospace industry are afew examples where fluid systems are of critical importance. In fluidsystems, it is often desirable to control properties of a fluid flow inthe fluid system to improve a performance or efficiency of the fluidsystem or to control the fluid in the fluid system in manner that allowsthe fluid system to operate properly.

As an example, in the automotive industry, the demand for higher power,better fuel economy, and reduced emissions from automobiles calls forcontinued improvement of automobile components, in particular, the needfor reduced size, weight, and costs of automotive components “under thehood.” Additionally, the demand for power, fuel economy and reducedemissions often results in conflicting requirements for engineperformance. For example, higher power usually comes at the expense offuel economy and/or emissions. Therefore, engine components must alsohave flexible operating characteristics to achieve performance atdifferent speed ranges.

A significant number of components under the hood of an automobile servethe function of controlling fluid flow in a manner that relates toengine performance and emissions. Flow control devices are found indifferent parts of the engine and various engine subsystems includingthe fuel injection system, the air intake system, the cooling system,and the exhaust system.

For instance, the operating characteristics of the intake and exhaustvalves for the combustion chamber are important to engine performance.The intake valve opens at proper times to let air/fuel mixture into thecombustion chamber and the exhaust valve opens at proper times to letout the exhaust. The valve timing and lift (amount of valve opening)characteristics of an engine has a major influence on engine performanceat different speed ranges. Current engines have fixed valve timing andlift so performance is a compromise between power and fuel economy. Theengine performance at different speeds can be optimized by employingvariable timing and valve lift. However, conventional actuatortechnology, such as solenoids and hydraulics, are expensive, heavy, andcomplex at the power levels required to actuate intake and exhaustvalves. Thus, variable timing and valve lift has not been heavilyutilized in the automotive industry. The limitations of conventionalactuator technology, such as cost and weight, are important in manyfluid control applications besides the automotive industry. Forinstance, weight and cost are usually critical considerations inaerospace applications.

New high-performance polymers capable of converting electrical energy tomechanical energy, and vice versa, are now available for a wide range ofenergy conversion applications. One class of these polymers,electroactive elastomers (also called dielectric elastomers,electroelastomers, or EPAM), is gaining wider attention. Electroactiveelastomers may exhibit high energy density, stress, andelectromechanical coupling efficiency. The performance of these polymersis notably increased when the polymers are prestrained in area. Forexample, a 10-fold to 25-fold increase in area significantly improvesperformance of many electroactive elastomers. Actuators and transducersproduced using these materials can be significantly cheaper, lighter andhave a greater operation range as compared to conventional technologiesused in fluid control applications.

Thus, improved techniques for implementing these high-performancepolymers in fluid control applications would be desirable.

SUMMARY OF THE INVENTION

The invention describes devices for controlling fluid flow, such asvalves. The devices may include one or more electroactive polymertransducers with an electroactive polymer that deflects in response toan application of an electric field. The electroactive polymer may be incontact with a fluid where the deflection of the electroactive polymermay be used to change a characteristic of the fluid. Some of thecharacteristic of the fluid that may be changed include but are notlimited to 1) a fluid flow rate, 2) a fluid flow direction, 3) a fluidflow vorticity, 4) a fluid flow momentum, 5) a fluid flow mixing rate,6) a fluid flow turbulence rate, 7) a fluid flow energy, 8) a fluid flowthermodynamic property. The electroactive polymer may be a portion of asurface of a structure that is immersed in an external fluid flow, suchas the surface of an airplane wing or the electroactive polymer may be aportion of a surface of a structure used in an internal flow, such as abounding surface of a fluid conduit.

One aspect of the present invention provides device for controlling afluid. The device may be generally characterized as comprising: 1) oneor more transducers, each transducer comprising at least two electrodesand a electroactive polymer in electrical communication with the atleast two electrodes wherein a portion of the electroactive polymer isarranged to deflect from a first position with a first area to a secondposition with a second area in response to a change in electric field;2) at least one surface in contact with a fluid and operatively coupledto the one or more transducers wherein the deflection of the portion ofthe electroactive polymer causes a change in a characteristic of thefluid that is transmitted to the fluid via the one surface. Thecharacteristic of the fluid that may be changed includes but is notlimited to a fluid flow rate, 2) a fluid flow direction, 3) a fluid flowvorticity, 4) a fluid flow momentum, 5) a fluid flow mixing rate, 6) afluid flow turbulence rate, 7) a fluid flow energy, 8) a fluid flowthermodynamic property.

In particular embodiments, the deflection of the portion of theelectroactive polymer may change the one surface from a first shape to asecond shape. For instance, the one surface may expand to form one of aballoon-like shape, a hemispherical shape, a cylinder shape, or ahalf-cylinder shape. The one surface may be operatively coupled to theone or more transducers via a mechanical linkage. Further, the onesurface may be an outer surface of the portion of the electroactivepolymer.

The fluid may be compressible, incompressible or combinations thereof.The fluid may also be one of homogeneous or heterogeneous. Further, thefluid may behave as a Newtonian fluid or a non-Newtonian fluid. Thefluid is selected from the group consisting of a mixture, a slurry, asuspension, a mixture of two or more immiscible liquids and combinationsthereof. The fluid may include one or constituents in a state selectedfrom the group consisting of a liquid, a gas, a plasma, a solid, a phasechange and combinations thereof.

In a particular embodiment, the fluid may flow over the one surface. Thedeflection of the portion of the electroactive polymer may change theshape of the one surface to alter a property of a viscous flow layer ofthe fluid flow or to alter a property of an inviscid flow layer of thefluid flow. Further, the deflection of the portion of the electroactivepolymer may change the shape of the one surface to promote mixing ofconstituents in the fluid or to block the fluid flow. In addition, thedeflection of the portion of the electroactive polymer may cause achange in temperature of the one surface or a change in a surfaceroughness of the one surface. For example, the one surface may furthercomprise an array of microscopic electroactive polymer elements where adeflection of the microscopic electroactive polymer elements from afirst position to a second position changes a surface roughness of theone surface. Yet further, the deflection of the portion of theelectroactive polymer may cause the one surface to stretch or contractto alter a relative smoothness of the one surface where the relativesmoothness of the one surfaces affects a drag on a fluid flowing overthe one surface.

In other embodiment, the device may further comprise a fluid conduitconfigured to allow fluid to flow from an inlet of the fluid conduit toan exit of the fluid conduit and pass over the one surface between theinlet and the exit and wherein a bounding surface of the fluid conduitseparates the fluid from an outer environment. In this case, the onesurface may be an outer surface of the portion of the electroactivepolymer and also a portion of the bounding surface of the fluid conduit.The deflection of the portion of the electroactive polymer may cause ashape of the bounding surface of the fluid conduit to change. Forinstance, the shape of the fluid conduit may be changed to increase thedistance the fluid travels from the inlet to the exit. Further, theshape of the fluid conduit may change dynamically as a function of time.For example, the shape of the fluid conduit may be changed to increaseor decrease a cross-sectional area of a section of the fluid conduitwhere the shape of the cross-sectional area is selected from the groupconsisting of circular, ovular, rectangular and polygonal. The shapes oftwo or more portions the bounding surface of the fluid conduit may bechanged independently in response to the deflection of the portion ofthe polymer in the one or more transducers. Also, the deflection of theportion of the polymer causes a bounding surface of the polymer torotate torsionally.

In yet other embodiments, the bounding surface of the fluid conduit maybe comprised of a rolled electroactive polymer transducer with a hollowcenter. Further, one or more transducers may be arranged to deflect in amanner that pinches a portion of an outer perimeter of a section of thefluid conduit to block the fluid flow in the conduit where the one ormore transducers may be configured in a sleeve designed to fit over theouter perimeter of a section of the fluid conduit. In anotherembodiment, the deflection in the portion of the electroactive polymermay cause the one surface to expand to block the flow in the fluidconduit, to expand to increase or decrease the flow in the fluidconduit, to expand to divert flow in the fluid conduit from a firstchannel to a second channel connected to the fluid conduit.

In a particular embodiment, a portion of the fluid conduit is a nozzlebody for expanding the fluid from a throat area in the fluid conduit toan exit of the nozzle body. The deflection in the portion of theelectroactive polymer may cause the nozzle body to expand or contract tochange an expansion rate of the fluid in the nozzle body and a velocityprofile of the fluid at the exit of the nozzle body. Further, thedeflection of the portion of the electroactive polymer causes a crosssectional shape of the nozzle body to change from a first shape to asecond shape. In addition, the deflection of the portion of theelectroactive polymer causes a cross section shape of the throat area tochange from a first shape to a second shape. Yet further, the deflectionof the portion of the electroactive polymer causes the nozzle body tobend to change a direction of the fluid exiting the nozzle.

The device may also comprise one or more sensors connected to the devicefor detecting a property of the fluid where the property of the fluid isselected from the group consisting of a temperature, a pressure, aconcentration of a constituent of the fluid, a velocity of the fluid, adensity of the fluid and flow rate of the fluid. Further, the device mayalso include one or mores sensors connected to the device for monitoringone or more of a temperature, a pressure, the deflection of the portionof the polymer, a charge on the portion of the polymer, a voltage on theportion of the polymer. In addition, the device may comprise a logicdevice for at least one of: 1) controlling operation of the transducer,2) monitoring one or more sensors, 3) communicating with other devices,and 4) combinations thereof. Also, the device may comprise conditioningelectronics designed or configured to perform one or more of thefollowing functions for the electroactive polymer: voltage step-up,voltage step-down and charge control.

In other embodiments, the polymer may comprise a material selected fromthe group consisting of a silicone elastomer, an acrylic elastomer, apolyurethane, a copolymer comprising PVDF, and combinations thereof. Thedevice may include an insulation barrier designed or configured toprotect the one surface from constituents of the fluid in contact withthe one surface or one or more support structures designed or configuredto attach to the one or more transducers. The electroactive polymer maybe elastically pre-strained at the first position to improve amechanical response of the electroactive polymer between the firstposition and second position, may an elastic modulus below about 100 MPaand may have an elastic area strain of at least about 10 percent betweenthe first position and the second position.

The polymer may comprise a multilayer structure where the multilayerstructure comprises two or more layers of electroactive polymers. Thedevice may be fabricated on a semiconductor substrate. The device may bea valve. Further, the one surface is part of a surface of vane forcontrolling a direction of a flow of the fluid where the deflection ofthe portion of the polymer changes an orientation of the vane in thefluid flow.

Another aspect of the present invention provides a valve. The valve maybe generally characterized as comprising 1) one or more transducers,each transducer comprising at least two electrodes and a electroactivepolymer in electrical communication with the at least two electrodeswherein a portion of the electroactive polymer is arranged to deflectfrom a first position with a first area to a second position with asecond area in response to a change in electric field; 2) an inlet andan exit for allowing a fluid to enter the valve and exit the valve; 3) aflow path between the inlet and exit that allows a fluid to pass throughthe valve; 4) a structure operatively coupled to the one or moretransducers wherein the deflection of the portion of the electroactivepolymer causes an operating position of the structure to change andwherein a change in the operating position of the structure changes theflow path. The structure may be designed to have two operating positionswhere when structure is in the first operating position, the flow pathis closed and where when the structure is in the second operatingposition, the flow path is open. Also, the structure may be designed tohave a plurality of operating positions. The deflection of the portionof the electroactive polymer may change the structure from a first shapeto a second shape.

In particular embodiments, the change in the operating position of thestructure may change a cross-sectional area of the flow path for atleast one location along the flow path. The valve may also comprise avalve seat wherein the deflection of the portion of the polymer causesthe structure to contact the valve seat. The valve may be a diaphragmvalve and the structure may be a diaphragm. When the valve is adiaphragm valve, the structure may be the electroactive polymer in ashape of a diaphragm. In general, the electroactive polymer may be apart of the structure. The valve may also be a needle valve where thestructure is a conical in shape. The valve may be a ball valve where thestructure is spherical in shape or a plug valve where the structure isplug-shaped. In general, the valve may be one of a check valve, abuttery fly valve, a pressure relief valve, a needle valve, a controlvalve, a slot valve, a rotary valve, engine in-take valve and an engineexhaust valve.

In other embodiments, the structure may further include a fluid conduitthat is a section of the flow path. The deflection of the portion of thepolymer causes the structure to rotate from a first operating positionto a second operating position where in the first operating position thefluid conduit in the structure is aligned with the flow path outside ofthe structure and the flow path through the valve is open. In the secondoperating position, the fluid conduit may not be aligned with the flowpath outside of the structure and the flow path through the valve isblocked. In addition, the deflection of the portion of the polymer maycause the structure to move linearly from a first operating position toa second operating position. When the structure is in the firstoperating position, the fluid conduit in the structure may be alignedwith the flow path outside of the structure and the flow path throughthe valve is open. When the structure is in the second operatingposition, the fluid conduit is not aligned with the flow path outside ofthe structure and the flow path through the valve is blocked. The valvemay be a slot valve and the fluid conduit is a slot.

In yet other embodiments, the structure is an electroactive polymer rollwhere a section of the flow path is through the center of the polymerroll. Further, the portion of the electroactive polymer may be abounding surface in the flow path. The valve may comprise one or moresensors where an input signal from the one or more sensors is used todetermine the operating position of the structure. The valve may be amulti-port valve and the operating position of the structure allows theflow path to align with one of a plurality of ports. The valve mayfurther comprise a logic device for at least one of: 1) controllingoperation of the valve, 2) monitoring one or more sensors, 3)communicating with other devices, and 4) combinations thereof orconditioning electronics designed or configured to perform one or moreof the following functions for the electroactive polymer: voltagestep-up, voltage step-down and charge control. The valve may include aforce mechanism, which provides a force in a direction opposite to adirection of a second force applied to the structure by the deflectionof the portion of the electroactive polymer. The force mechanism may bea spring.

These and other features and advantages of the present invention will bedescribed in the following description of the invention and associatedfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a top view of a transducer portion before andafter application of a voltage, respectively, in accordance with oneembodiment of the present invention.

FIGS. 2A-2F illustrate Electroactive Polymer (EPAM) flow control deviceswhere the EPAM devices comprise a portion of the bounding surface ofsurface of a fluid conduit.

FIGS. 2G-2J illustrate EPAM flow control devices where the EPAM deviceis used to control a flow rate in a fluid conduit.

FIG. 2K illustrate an EPAM flow control device for mixing and dispensingof a fluid.

FIGS. 2L and 2M illustrate an EPAM flow control device used to control adirection of a fluid traveling through a conduit.

FIG. 2N illustrate an EPAM flow control devices used to change a surfaceroughness of a fluid conduit, impress wave patterns in a flow in a fluidconduit or block a fluid conduit.

FIGS. 2O-2R illustrate an EPAM flow control devices used in a nozzleapplication.

FIGS. 3A-3M illustrate an EPAM flow control devices used in a variety ofdifferent valve applications.

FIGS. 4A-4D illustrate a rolled electroactive polymer device inaccordance with one embodiment of the present invention.

FIG. 4E illustrates an end piece for the rolled electroactive polymerdevice of FIG. 2A in accordance with one embodiment of the presentinvention.

FIG. 4F illustrates a bending transducer for providing variablestiffness based on structural changes related to polymer deflection inaccordance with one embodiment of the present invention.

FIG. 4G illustrates the transducer of FIG. 4A with a 90 degree bendingangle.

FIG. 4H illustrates a bow device suitable for providing variablestiffness in accordance with another embodiment of the presentinvention.

FIG. 4I illustrates the bow device of FIG. 4C after actuation.

FIG. 4J illustrates a monolithic transducer comprising a plurality ofactive areas on a single polymer in accordance with one embodiment ofthe present invention.

FIG. 4K illustrates a monolithic transducer comprising a plurality ofactive areas on a single polymer, before rolling, in accordance with oneembodiment of the present invention.

FIG. 4L illustrates a rolled transducer that produces two-dimensionaloutput in accordance with one environment of the present invention.

FIG. 4M illustrates the rolled transducer of FIG. 4L with actuation forone set of radially aligned active areas.

FIG. 4N illustrates an electrical schematic of an open loop variablestiffness/damping system in accordance with one embodiment of thepresent invention.

FIG. 5A is block diagram of one or more active areas connected to powerconditioning electronics.

FIG. 5B is a circuit schematic of a device employing a rolledelectroactive polymer transducer for one embodiment of the presentinvention.

FIG. 6 is a schematic of a sensor employing an electroactive polymertransducer according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described in detail with reference to a fewpreferred embodiments as illustrated in the accompanying drawings. Inthe following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art, that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process steps and/or structureshave not been described in detail in order to not unnecessarily obscurethe present invention.

Electroactive Polymers

Before describing electroactive polymer (EPAM) flow control devices ofthe present invention, the basic principles of electroactive polymerconstruction and operation will first be illuminated in regards to FIG.1A and FIG. 1B. Embodiments of flow control devices and systems of thepresent invention are described with respect to FIGS. 2A-2M and 3A-3M inthe following section. The transformation between electrical andmechanical energy in devices of the present invention is based on energyconversion of one or more active areas of an electroactive polymer.Electroactive polymers are capable of converting between mechanicalenergy and electrical energy. In some cases, an electroactive polymermay change electrical properties (for example, capacitance andresistance) with changing mechanical strain.

To help illustrate the performance of an electroactive polymer inconverting between electrical energy and mechanical energy, FIG. 1Aillustrates a top perspective view of a transducer portion 10 inaccordance with one embodiment of the present invention. The transducerportion 10 comprises a portion of an electroactive polymer 12 forconverting between electrical energy and mechanical energy. In oneembodiment, an electroactive polymer refers to a polymer that acts as aninsulating dielectric between two electrodes and may deflect uponapplication of a voltage difference between the two electrodes (a‘dielectric elastomer’). Top and bottom electrodes 14 and 16 areattached to the electroactive polymer 12 on its top and bottom surfaces,respectively, to provide a voltage difference across polymer 12, or toreceive electrical energy from the polymer 12. Polymer 12 may deflectwith a change in electric field provided by the top and bottomelectrodes 14 and 16. Deflection of the transducer portion 10 inresponse to a change in electric field provided by the electrodes 14 and16 is referred to as ‘actuation’. Actuation typically involves theconversion of electrical energy to mechanical energy. As polymer 12changes in size, the deflection may be used to produce mechanical work.

Without wishing to be bound by any particular theory, in someembodiments, the polymer 12 may be considered to behave in anelectrostrictive manner. The term electrostrictive is used here in ageneric sense to describe the stress and strain response of a materialto the square of an electric field. The term is often reserved to referto the strain response of a material in an electric field that arisesfrom field induced intra-molecular forces but we are using the term moregenerally to refer to other mechanisms that may result in a response tothe square of the field. Electrostriction is distinguished frompiezoelectric behavior in that the response is proportional to thesquare of the electric field, rather than proportional to the field. Theelectrostriction of a polymer with compliant electrodes may result fromelectrostatic forces generated between free charges on the electrodes(sometimes referred to as “Maxwell stress”) and is proportional to thesquare of the electric field. The actual strain response in this casemay be quite complicated depending on the internal and external forceson the polymer, but the electrostatic pressure and stresses areproportional to the square of the field.

FIG. 1B illustrates a top perspective view of the transducer portion 10including deflection. In general, deflection refers to any displacement,expansion, contraction, torsion, linear or area strain, or any otherdeformation of a portion of the polymer 12. For actuation, a change inelectric field corresponding to the voltage difference applied to or bythe electrodes 14 and 16 produces mechanical pressure within polymer 12.In this case, the unlike electrical charges produced by electrodes 14and 16 attract each other and provide a compressive force betweenelectrodes 14 and 16 and an expansion force on polymer 12 in planardirections 18 and 20, causing polymer 12 to compress between electrodes14 and 16 and stretch in the planar directions 18 and 20.

Electrodes 14 and 16 are compliant and change shape with polymer 12. Theconfiguration of polymer 12 and electrodes 14 and 16 provides forincreasing polymer 12 response with deflection. More specifically, asthe transducer portion 10 deflects, compression of polymer 12 brings theopposite charges of electrodes 14 and 16 closer and the stretching ofpolymer 12 separates similar charges in each electrode. In oneembodiment, one of the electrodes 14 and 16 is ground. For actuation,the transducer portion 10 generally continues to deflect untilmechanical forces balance the electrostatic forces driving thedeflection. The mechanical forces include elastic restoring forces ofthe polymer 12 material, the compliance of electrodes 14 and 16, and anyexternal resistance provided by a device and/or load coupled to thetransducer portion 10, etc. The deflection of the transducer portion 10as a result of an applied voltage may also depend on a number of otherfactors such as the polymer 12 dielectric constant and the size ofpolymer 12.

Electroactive polymers in accordance with the present invention arecapable of deflection in any direction. After application of a voltagebetween the electrodes 14 and 16, the electroactive polymer 12 increasesin size in both planar directions 18 and 20. In some cases, theelectroactive polymer 12 is incompressible, e.g. has a substantiallyconstant volume under stress. In this case, the polymer 12 decreases inthickness as a result of the expansion in the planar directions 18 and20. It should be noted that the present invention is not limited toincompressible polymers and deflection of the polymer 12 may not conformto such a simple relationship.

Application of a relatively large voltage difference between electrodes14 and 16 on the transducer portion 10 shown in FIG. 1A will causetransducer portion 10 to change to a thinner, larger area shape as shownin FIG. 1B. In this manner, the transducer portion 10 convertselectrical energy to mechanical energy. The transducer portion 10 mayalso be used to convert mechanical energy to electrical energy.

For actuation, the transducer portion 10 generally continues to deflectuntil mechanical forces balance the electrostatic forces driving thedeflection. The mechanical forces include elastic restoring forces ofthe polymer 12 material, the compliance of electrodes 14 and 16, and anyexternal resistance provided by a device and/or load coupled to thetransducer portion 10, etc. The deflection of the transducer portion 10as a result of an applied voltage may also depend on a number of otherfactors such as the polymer 12 dielectric constant and the size ofpolymer 12.

In one embodiment, electroactive polymer 12 is pre-strained. Pre-strainof a polymer may be described, in one or more directions, as the changein dimension in a direction after pre-straining relative to thedimension in that direction before pre-straining. The pre-strain maycomprise elastic deformation of polymer 12 and be formed, for example,by stretching the polymer in tension and fixing one or more of the edgeswhile stretched. Alternatively, as will be described in greater detailbelow, a mechanism such as a spring may be coupled to different portionsof an electroactive polymer and provide a force that strains a portionof the polymer. For many polymers, pre-strain improves conversionbetween electrical and mechanical energy. The improved mechanicalresponse enables greater mechanical work for an electroactive polymer,e.g., larger deflections and actuation pressures. In one embodiment,prestrain improves the dielectric strength of the polymer. In anotherembodiment, the prestrain is elastic. After actuation, an elasticallypre-strained polymer could, in principle, be unfixed and return to itsoriginal state.

In one embodiment, pre-strain is applied uniformly over a portion ofpolymer 12 to produce an isotropic pre-strained polymer. By way ofexample, an acrylic elastomeric polymer may be stretched by 200 to 400percent in both planar directions. In another embodiment, pre-strain isapplied unequally in different directions for a portion of polymer 12 toproduce an anisotropic pre-strained polymer. In this case, polymer 12may deflect greater in one direction than another when actuated. Whilenot wishing to be bound by theory, it is believed that pre-straining apolymer in one direction may increase the stiffness of the polymer inthe pre-strain direction. Correspondingly, the polymer is relativelystiffer in the high pre-strain direction and more compliant in the lowpre-strain direction and, upon actuation, more deflection occurs in thelow pre-strain direction. In one embodiment, the deflection in direction18 of transducer portion 10 can be enhanced by exploiting largepre-strain in the perpendicular direction 20. For example, an acrylicelastomeric polymer used as the transducer portion 10 may be stretchedby 10 percent in direction 18 and by 500 percent in the perpendiculardirection 20. The quantity of pre-strain for a polymer may be based onthe polymer material and the desired performance of the polymer in anapplication. Pre-strain suitable for use with the present invention isfurther described in commonly owned, U.S. Pat. No. 6,812,624, which isincorporated by reference for all purposes.

Generally, after the polymer is pre-strained, it may be fixed to one ormore objects or mechanisms. For a rigid object, the object is preferablysuitably stiff to maintain the level of pre-strain desired in thepolymer. A spring or other suitable mechanism that provides a force tostrain the polymer may add to any prestrain previously established inthe polymer before attachment to the spring or mechanisms, or may beresponsible for all the prestrain in the polymer. The polymer may befixed to the one or more objects or mechanisms according to anyconventional method known in the art such as a chemical adhesive, anadhesive layer or material, mechanical attachment, etc.

Transducers and pre-strained polymers of the present invention are notlimited to any particular rolled geometry or type of deflection. Forexample, the polymer and electrodes may be formed into any geometry orshape including tubes and multi-layer rolls, rolled polymers attachedbetween multiple rigid structures, rolled polymers attached across aframe of any geometry—including curved or complex geometries, across aframe having one or more joints, etc. Similar structures may be usedwith polymers in flat sheets. Deflection of a transducer according tothe present invention includes linear expansion and compression in oneor more directions, bending, axial deflection when the polymer isrolled, deflection out of a hole provided on an outer cylindrical aroundthe polymer, etc. Deflection of a transducer may be affected by how thepolymer is constrained by a frame or rigid structures attached to thepolymer.

Materials suitable for use as an electroactive polymer with the presentinvention may include any substantially insulating polymer or rubber (orcombination thereof) that deforms in response to an electrostatic forceor whose deformation results in a change in electric field. One suitablematerial is NuSil CF19-2186 as provided by NuSil Technology ofCarpenteria, Calif. Other exemplary materials suitable for use as apre-strained polymer include silicone elastomers, acrylic elastomerssuch as VHB 4910 acrylic elastomer as produced by 3M Corporation of St.Paul, Minn., polyurethanes, thermoplastic elastomers, copolymerscomprising PVDF, pressure-sensitive adhesives, fluoroelastomers,polymers comprising silicone and acrylic moieties, and the like.Polymers comprising silicone and acrylic moieties may include copolymerscomprising silicone and acrylic moieties, polymer blends comprising asilicone elastomer and an acrylic elastomer, for example. Combinationsof some of these materials may also be used as the electroactive polymerin transducers of this invention.

Materials used as an electroactive polymer may be selected based on oneor more material properties such as a high electrical breakdownstrength, a low modulus of elasticity—(for large or small deformations),a high dielectric constant, etc. In one embodiment, the polymer isselected such that is has an elastic modulus at most about 100 MPa. Inanother embodiment, the polymer is selected such that is has a maximumactuation pressure between about 0.05 MPa and about 10 MPa, andpreferably between about 0.3 MPa and about 3 MPa. In another embodiment,the polymer is selected such that is has a dielectric constant betweenabout 2 and about 20, and preferably between about 2.5 and about 12.

An electroactive polymer layer in transducers of the present inventionmay have a wide range of thicknesses. In one embodiment, polymerthickness may range between about 1 micrometer and 2 millimeters.Polymer thickness may be reduced by stretching the film in one or bothplanar directions. In many cases, electroactive polymers of the presentinvention may be fabricated and implemented as thin films. Thicknessessuitable for these thin films may be below 50 micrometers.

As electroactive polymers of the present invention may deflect at highstrains, electrodes attached to the polymers should also deflect withoutcompromising mechanical or electrical performance. Generally, electrodessuitable for use with the present invention may be of any shape andmaterial provided that they are able to supply a suitable voltage to, orreceive a suitable voltage from, an electroactive polymer. The voltagemay be either constant or varying over time. In one embodiment, theelectrodes adhere to a surface of the polymer. Electrodes adhering tothe polymer are preferably compliant and conform to the changing shapeof the polymer. Correspondingly, the present invention may includecompliant electrodes that conform to the shape of an electroactivepolymer to which they are attached. The electrodes may be only appliedto a portion of an electroactive polymer and define an active areaaccording to their geometry. Several examples of electrodes that onlycover a portion of an electroactive polymer will be described in furtherdetail below.

Various types of electrodes suitable for use with the present inventionare described in commonly owned, U.S. Pat. No. 6,812,624, which waspreviously incorporated by reference above. Electrodes described thereinand suitable for use with the present invention include structuredelectrodes comprising metal traces and charge distribution layers,textured electrodes comprising varying out of plane dimensions,conductive greases such as carbon greases or silver greases, colloidalsuspensions, high aspect ratio conductive materials such as carbonfibrils and carbon nanotubes, and mixtures of ionically conductivematerials.

Materials used for electrodes of the present invention may vary.Suitable materials used in an electrode may include graphite, carbonblack, colloidal suspensions, thin metals including silver and gold,silver filled and carbon filled gels and polymers, and ionically orelectronically conductive polymers. In a specific embodiment, anelectrode suitable for use with the present invention comprises 80percent carbon grease and 20 percent carbon black in a silicone rubberbinder such as Stockwell RTV60-CON as produced by Stockwell Rubber Co.Inc. of Philadelphia, Pa. The carbon grease is of the type such asNyoGel 756G as provided by Nye Lubricant Inc. of Fairhaven, Mass. Theconductive grease may also be mixed with an elastomer, such as siliconelastomer RTV 118 as produced by General Electric of Waterford, N.Y., toprovide a gel-like conductive grease.

It is understood that certain electrode materials may work well withparticular polymers and may not work as well for others. By way ofexample, carbon fibrils work well with acrylic elastomer polymers whilenot as well with silicone polymers. For most transducers, desirableproperties for the compliant electrode may include one or more of thefollowing: low modulus of elasticity, low mechanical damping, lowsurface resistivity, uniform resistivity, chemical and environmentalstability, chemical compatibility with the electroactive polymer, goodadherence to the electroactive polymer, and the ability to form smoothsurfaces. In some cases, a transducer of the present invention mayimplement two different types of electrodes, e.g. a different electrodetype for each active area or different electrode types on opposing sidesof a polymer.

2. EPAM Flow Control Devices

In the present, EPAM flow control devices may be used to alter one ormore characteristics of an internal flow, such as the flow of a fluid asit moves through a conduit or an external flow, such as the flow over anairplane wing. An EPAM flow control device, refers to a device thatregulates, affects or controls fluidic communication of gases, liquidsand/or loose particles through or around one or more structures andincludes one or more EPAM transducers. The characteristics of the flowmay be altered by changing the properties of one or more surfaces incontact with the fluid via operation of the one or more EPAMtransducers. Some characteristics of a fluid that may be altered includebut are not limited to 1) a flow rate, 2) a flow direction, 3) a flowvorticity, 4) a flow momentum or velocity, 5) a flow mixing rate, 6) aflow turbulence rate, 7) a flow energy and 8) a flow thermodynamicproperty. Typically, the EPAM flow control devices described in thepresent invention do not provide a driving force, such as a pressuregradient, that moves the bulk fluid between locations. However, thepresent invention is not so limited and may also be used to provide adriving force to the fluid.

The fluids of the present invention may include materials in states of aliquid, a gas, a plasma, a phase change, a solid or combinationsthereof. The fluid may behave as a non-Newtonian fluid or a Newtonianfluid. Further, the fluid may be homogenous or heterogeneous. Also, thefluid may be incompressible or compressible. Examples of fluids in thepresent invention include but are not limited to 1) mixtures, 2)slurries, 3) suspensions and 4) flows of two or more immiscible liquids.

FIGS. 2A-2F illustrate EPAM flow control devices where the EPAM comprisea portion of the bounding surface of surface of a fluid conduit used inan internal flow system. The fluid conduit separates the fluid in theconduit from an external environment. Although not shown, when the EPAMflow control devices may be used in an external flow where the EPAMcomprises a bounding surface of a structure in the external flow.

In FIG. 2A, a section of a fluid conduit 300 is shown. The fluid conduit300 includes an inlet 304 and an exit 305. A general direction of a flowof a fluid inside the conduit is indicate by the arrows 306. The fluidconduit 300 may be a component in a larger fluid system. The fluidconduit is comprised of a bounding surface 303 that separates fluidflowing in the conduit 300 from an external environment. A cross section301 of the fluid conduit at the inlet is circular. However, in general,the cross section does not have to be circular and may be a polygon orother general shape with sides of varying length. In addition, the crosssectional shape may vary as a function of position in the fluid conduit300. Further, the bounding surface 303 does not necessarily have to beclosed. For instance, a trough may be used as a fluid conduit whereinportions of the conduit are open to an external environment.

One or more portions of the bounding surface 303 may be configured withEPAM devices. Portions of the EPAM devices serve as part of the boundingsurface 303 of the fluid conduit 300. In one embodiment, the entirebounding surface 303 may comprise an EPAM material. In anotherembodiment, EPAM material is integrated with one or more other materialsto form the bounding surface 303. The EPAM material may include one ormore layers or surface coatings depending on a compatibility of the EPAMmaterial with the fluid flowing in the conduit or a compatibility of theEPAM material with the external environment. The fluid conduit 300 mayinclude interfaces that allow it to attach to other fluid conduits orcomponents in a fluid system in which it is applied. The EPAM devices ofthe present invention may be applied in fluid applications that vary insize from microscales, such as moving fluid on a silicon chip, tomacroscales, such as moving fluid in a large chemical plant.

Portions of the EPAM materials forming the bounding surface 303 may beconfigured with electrodes to allow the portions of the EPAM material toact as an EPAM transducer. In response to an electric field applied tothe EPAM material, such as a polymer, the EPAM material may bedeflected. Each EPAM transducer device may be independently controlledin its deflection. Thus, the bounding surface 303 may change shape as afunction of time to alter one or more of the characteristics flow in thefluid conduit 300.

In the Figure, two EPAM flow control devices, 308 and 309 are shown. TheEPAM flow control devices include one or more EPAM transducers. Variousdeflection positions denoted by the dashed lines, such as 310 and 311,of the EPAM flow control devices are shown. At rest, the active EPAMareas may be nearly tangential with the surrounding surfaces. When avoltage is applied, the EPAM areas expand inward. The inward expansion(as opposed to outward expansion when voltage is applied to EPAM) may beassured by having the outer pressure higher than the internal pressure.Alternately, one may use springs, foam, laminates of other polymers, orother techniques known in the prior art for biasing the EPAM to expandinward when a voltage is applied. For instance, when the flow controldevices 308 and 309 are at rest a cross sectional area 307 of theconduit between the EPAM flow control devices may be the same as thecross sectional area 301 of the inlet. Alternately, one may design anEPAM annulus that is normally contracted, and when voltage is applied itexpands outward to allow an increased flow. The outward expansion wouldbe assured in this case if the internal flow pressure is higher than thepressure of the outer environment, a common situation for pumped flows.

As the devices 308 and 309 deflect, for instance from an initialposition to positions 310 and 311, a circular cross-sectional area 307between the EPAM flow control devices may decrease. The cross section307 does not have to remain circular and may be of any shape dependingon the configuration of the EPAM flow control devices on the boundingsurface 303. After deflection of the devices 308 and 309 and dependingon the driving force in the flow, the constriction of the conduit 300between the EPAM flow control devices 308 may reduce the flow rate inthe conduit at the exit. For instance, the flow may become choked at307. The driving force for the flow may also be reduced in conjunctionwith the constriction to control the flow rate in the conduit. In someembodiments, the devices, 308 and 309, may sufficiently contracttogether to stop the flow in the conduction 300.

In another embodiment, the EPAM flow control devices, 308 and 309, maydeflect one at a time at some defined interval. The alternatedeflections of the EPAM devices may direct the flow near the deflectedsurface upward like a ramp into the main stream to promote mixing in thefluid in the conduit 300 if mixing is desirable. As another example,vibrations of the EPAM flow control devices, 308 and 309, at particularfrequencies may be used to increase the amount of turbulence in the flowif turbulence is desirable. Increased turbulence may change the velocityprofile in the fluid conduit and provide turbulent mixing.

In yet another embodiment, one or more EPAM flow control devices, suchas 308 or 309, on the bounding surface 303 may act as a heat exchangerto add or remove energy from the flow in the conduit 300. For instance,when it desired to cool the flow in the conduit 300 and the outerenvironment surrounding the conduit 300 is cooler than flow in theconduit, the EPAM flow control devices may include a heat exchangerallowing energy to be removed from the fluid in the fluid conduit 300.Adding or removing energy from the flow can change the thermodynamicproperties of the fluid flow, such as the pressure and temperature. Asan example, the deflections of the EPAM flow control devices, 308 and309, may circulate fluid in a second closed fluid system used inconjunction with the fluid conduit to add or remove energy from thefluid conduit 300. Some examples of heat exchangers that may be usedwith the present invention are described in commonly owned U.S. Pat. No.6,628,040, by Pelrine, et al., and entitled “Electroactive PolymerThermal Generators,” which is incorporated herein in its entirety andfor all purposes.

In FIG. 2B, a fluid conduit with one inlet 304 and two exits 312 and 313are shown. The fluid conduit is shaped like a “Y.” At the point in theconduit where it splits from a single channel to two channels, two EPAMactive areas, 310 and 311, are shown. The EPAM areas, 310 and 311, arepart of the bounding surface 303 of the fluid conduit. Deflections ofthe EPAM active areas, 310 and 311, are denoted by the dashed line. Thedeflections of the EPAM active areas, 310 and 311, may be used to 1)control the flow rate in each of the two channels, 2) divert the flow inthe conduit from one of the section to the other section or 3) blockboth channels. The flow diversion from one channel to other may beperformed by deflecting either active area, 310 or 311, to block one ofthe channels. The other channel may remain open with its EPAM activearea undeflected or partially deflected to allow the flow in conduit totravel through the open conduit. The partially deflected EPAM activearea may be used to control the flow rate in the unblocked channel.

FIGS. 2C-2F show a hollow EPAM flow control device 315 used as abounding surface 303 of a fluid conduit. In FIGS. 2C and 2D, the EPAMflow control device 315 has a diameter 317, an inlet 304, an exit 305and a fluid moving in a flow direction 306 from the inlet 304 to theexit 305. In one embodiment, the EPAM flow control device 315 may bedeflected to lengthen and decrease the diameter of the fluid conduit. InFIG. 2D, the EPAM flow control device 315 lengthens in a straight linealong the axis 316. The lengthening of the fluid conduit may changecharacteristics of the conduit, such as viscous dissipative forces likefrictional forces that depend on the length of the conduit, the flowrate in the conduit that depends on the cross-sectional area, andacoustic and vibration properties of the conduit that may depend on thelength of the pipe.

In regards to the acoustic properties of the EPAM flow control device315, a fluid conduit of a particular length may accommodate pressurewaves of particular frequencies. For instance, a sound generated by apipe in a pipe organ is proportional to the length of the pipe. Byincreasing or decreasing the length of the conduit by deflecting theEPAM material in the EPAM flow control device 315, acousticallyproperties of a flow traveling through the fluid conduit may be altered.For instance, an EPAM flow control device 315 may be used in anautomotive context such as in tail pipe used to channel exhaust gassesfrom an engine. By changing a actively the length of tail pipe using theEPAM flow control device, the acoustic properties of the EPAM tail pipemay be altered. In one embodiment, the EPAM tail pipe may be lengthenedor shortened according to the pressure of the exhaust gases beingemitted from the engine, which may vary depending on the operatingconditions of the engine.

In some embodiments, the EPAM flow control devices of the presentinvention, such as 315, may include one or more sensors that are used tomeasure flow conditions in the conduit, such as but not limited to flowrate sensors to measure the flow rate in the conduit, temperaturesensors to measure the temperature of the flow, concentration sensors tomeasure one or more constituents of the flow, pressure sensors tomeasure the total pressure of the flow or the partial pressures of oneor more constituents in the flow, acoustic sensors to measure acousticwaves in the flow and vibrational sensors to measure vibrations in thefluid conduit. The output obtained from the sensors may be used in acontrol algorithm to control the operation of the EPAM flow controldevice (e.g., the deflection of the active areas of the EPAM flow device315 as a function of time). The EPAM flow device 315 may include a logicdevice such as a microcontroller or a microprocessor for controllingoperation of the device.

The flow sensors used to control the operation of the flow device 315may be used to measure flow properties outside of the EPAM flow controldevice, such as upstream or downstream of the EPAM flow device 315 usedin a fluid system. Further, the operation of the EPAM flow controldevice, such as its length as a function of time, may be influenced bysensor inputs unrelated to flow properties. For instance, the length ofan EPAM tail pipe may be correlated to an RPM rate of an engineexhausting gasses through the tail pipe.

In particular embodiments, the EPAM flow control devices of the presentinvention, such as 315, may be designed to lengthen withoutsignificantly changing the diameter 317 or cross-sectional area fornon-circular cross sections. In another embodiment, the diameter 317 ofthe EPAM flow control device 315 may be increased or decreased along itslength without significantly changing the length of the flow device 315.

Lengthening without a diameter change may be performed using a springroll as described in the Pei citation below (U.S. Pat. No. 6,891,317). Asimple tube of EPAM without the spring and the circumferential prestrainmay naturally lengthen and increase its diameter. To lengthen andsimultaneously decrease diameter, one might have a free elastomer tubeinside a spring roll actuator—when the spring roll lengthens, the innerelastomer tube will lengthen and contract in diameter—but the springroll just lengthens. In yet another embodiment, a plurality of EPAM flowcontrol devices, such as 315, may be linked together via an interfacemechanism of some type, to generate a fluid conduit with a plurality ofsections that may be independently lengthened or shortened. Further, thediameter of the each of the linked sections may be independentlyincreased or decreased. A rolled EPAM transducer may be suitable to beused as these links. Details of the roll-type transducer, such as thespring roll, have been disclosed in commonly owned U.S. Pat. No.6,891,317, by Pei et al. and entitled, “Rolled Electroactive Polymers,”which is incorporated herein by reference in its entirety and for allpurposes.

In yet other embodiments, the EPAM flow control device 315 is notlimited to lengthening in a straight line, such as along its axis 316 inFIG. 2D. In FIGS. 2E-2F, the EPAM flow control device 315 may belengthened by deflecting it above and below the axis 316. For instance,in FIG. 2E, the EPAM flow control device 315 is deflected downward by adistance 318 from the axis 316. When the ends of the EPAM flow controldevice 315 are fixed and the EPAM flow control device 315 is lengthenedin deflection, the EPAM flow control device may deflect downwards orupwards. The deflection of the EPAM flow control device lengthens thefluid conduits, which may affect viscous dissipation forces and acousticproperties that are proportional to length. The deflection downwards orupwards may change the direction of flow, which may cause a loss ofmomentum within the flow as it turns. Dynamically deflecting the EPAMflow control device 315 upwards and downwards may provide mixing of theflow in the fluid conduit.

The shape of the EPAM fluid conduit may be complex. In FIG. 2F, a fluidconduit is shown with deflections above and below the axis 316. The flowdirection 306 starts parallel to the axis at the inlet 304 movesdownward below the axis and then turns upwards and finishes parallel tothe axis at the exit 305. The shape of the conduit, its length and thecross sectional area of the EPAM flow control device may changedynamically as function of time. As previously described above, flow andother sensors and an active control algorithms using input from the flowsensors may be used to control the shape, length and cross sectionalarea of area of the EPAM flow control device 315 as a function of time.

In one embodiment, one or more surfaces in the fluid conduit may beribbed or ridged in some manner. When the fluid conduit is lengthened orcontracted, the one or more surfaces may be stretched or shrunk tochange the rib or ridge height. The increase or decrease of the rib orridge height by the stretching may change the relative smoothness orroughness of the surface. The change in smoothness or roughness mayalter viscous properties of a boundary layer near the surface toincrease or decrease the drag on the fluid as it flows over the surface.

FIGS. 2G-2N show examples EPAM flow control devices that may be insertedinto a fluid conduit to alter one or more flow properties of the fluid.In these examples, the EPAM flow control devices are not primarily usedas part of the bounding surface of the fluid conduit. FIG. 2G shows oneexample of EPAM valve 325 of the present invention. In FIGS. 3A-3M moreexamples of EPAM valves of the present invention are described.

The EPAM valve 325 may comprise a frame 326 supporting a stretched EPAMpolymer 327. The EPAM polymer may be sufficiently pre-strained such thatdeflection of the polymer 327 results primarily in an in-plane movementtoward the center of the circular frame 326 indicated by the arrows,which decreases the diameter of the circle at the center of the valve.In another embodiment, the polymer may be deflected both outwards andtowards the center of the circle to increase or decrease the diameter ofthe circle at the center of the valve. The four electrodes 328 maycontrol the deflection of the polymer 327. In one embodiment, the fourelectrodes 328 may be used to deflect four active portions of thepolymer independently to provide non-circular shapes at the center ofthe valve with different areas.

A stop 330, which may be shaped as a sphere or a cylinder for instance,may be located in the center of the EPAM valve 325. The stop 330 may besupported by support members 329 connected to the polymer 327, frame 326or both. The EPAM valve 325 may be designed to deflect the polymer 327towards the center of the device and close around the stop 330.

In FIG. 2H, the EPAM valve 325 is shown inserted in a fluid conduit. Thefluid conduit has an inlet 304 and an exit 305 with a flow direction 306moving from the inlet to the exit. The frame of the EPAM valve may makeup a small portion of the bounding surface 303 or the EPAM valve may beinserted within the bounding surface 303. In FIG. 2H, the valve is showninserted perpendicular to the flow although the present invention is notlimited to a valve orientated perpendicular to the flow.

By increasing or decreasing the area of the EPAM valve 325, the flowrate in the fluid conduit may be controlled. When closed around the stop330, the flow rate may be reduced to zero. In some embodiments, the EPAMvalve 325 may not include a stop 330 or support structure in its center.In this embodiment, the cross sectional area at the center of the valvemay vary between a maximum and a minimum allowing a maximum and minimumflow rate to be specified. The amount of deflection of the polymer 327,which is a function of a strength of an electric field applied to thepolymer, may be used to determine the cross sectional area of the valveand hence the flow rate through the valve.

FIG. 2I shows an array 343 four EPAM valves 325 in a square mountingplate 331. The four valves 325 may be independently controlled. In oneembodiment, the mounting plate 331 may be used in a square duct tocontrol flow rate in the duct. In another embodiment, the four valves325 may be connected to four different feed lines to independentlycontrol flow in each of the lines such an embodiment is shown in FIG.2J. The frame 326 and mounting plate 331 may be rigid or themselvesflexible, and if many EPAM valves 325 are incorporated the effectiveporosity of the frame and mounting plate structure can be variedelectronically using the EPAM elements.

In FIG. 2J, two feed lines, 332 and 333, are shown connected to thevalves 325 in mounting plate 331. The valves are connected to twonozzles 334 and 335. The valves 325 may be used to control a flow ratein the nozzles 334 and 335 to produce an amount of spray from eachnozzle or a size of a droplet from each nozzle. For instance, EPAMvalves 325 may be used in an inkjet printer head to control droplet sizein the head. In one embodiment, the nozzles, 335 and 336, may also becomprised of an EPAM polymer. A length of the nozzle and its crosssectional area may be altered by deflecting the EPAM polymer in thenozzles. Changing the length of the nozzle and its cross sectional areamay be used to change the properties of the flow as it exits the nozzle,such as its velocity as it exits the nozzle or a resultant flow pattern.Further, by deflecting the polymer, a direction of the nozzle and hencethe flow direction of the fluid exiting the nozzle may also be changed.Details of EPAM nozzles are described in more detail with respect toFIGS. 2O-2R.

The EPAM flow control devices of the present invention may be used formixing and dispensing of a fluid. In FIG. 2K, an EPAM mixing device 341is shown. The EPAM mixing device 341 comprises an EPAM diaphragm 342connected to a support structure 339 to create a mixing chamber 340. Twofeed lines 332 and 333 provide fluid inputs for the chamber 340 and anoutput line 337 provides an outlet to the chamber 340 for a mixture.EPAM valves 325 are used to control the input and output of fluid to andfrom the chamber 340.

In one embodiment, the EPAM valves to each of the feed lines, 332 and333 may be opened to allow different fluids in each of the feed lines toenter the mixing chamber. The output feed line may be closed. A ratio ofthe fluids in each feed line may be varied by changing a valve diameterto increase or decrease a flow rate in each feed line and/or by a lengthof time each valve 325 to the feed lines are open. In one embodiment,the EPAM diaphragm 342 may expand to help draw fluid into the mixingchamber 340. In another embodiment, the fluid in the feed lines is underpressure and enters the mixing chamber via this pressure. The presentinvention is not limited two feed lines and a plurality of lines may beconnected to the mixing chamber 340. For instance, for a paint mixer,three feed lines, each providing one of the primary colors, may be used

After the fluids from the feed lines are in the mixing chamber 341, theEPAM diaphragm may deflect up and down at varying frequencies to mix thefluid in the chamber. The deflection pattern applied to the diaphragm342 may be quite complex. For instance, portions of the diaphragm maydeflect at different rates to promote mixing. After a predeterminedinterval of mixing, the valve 325 to the output feed line 337 may openand the diaphragm may deflect to dispense the mixed fluid from themixing chamber 341. In one embodiment, the mixing device 341 may includea purge fluid feed line and a purge fluid output line. The purge fluidmay be used to clean out fluid residues remaining in the mixing chamber340.

In one embodiment, the mixing device 341 may not include input feedlines. The mixing chamber may include a pre-mixed fluid that is simplydispensed from the device. For instance, antibiotics in an IV line.Using the device 341 as an IV dispenser, the fluid in the chamber may bedispensed in a controlled manner without having to rely on gravity todispense the fluid from the chamber and eliminating the requirement ofhaving to hold the IV bag in a raised position above a patient. Inanother embodiment, the mixing device may include a number of fluidconstituents that remain un-mixed or tend to separate. As an example,the mixing chamber 341 may include a number of fluid and solidconstituents that are sealed in packets, such as medicine. When themixing device 341 is activated, the sealed packets are broken and aremixed together in the mixing chamber. The mixture is then dispensed viathe output line 337.

In FIGS. 2L and 2M, EPAM flow control devices used to change thedirection of a fluid in a flow are shown. In FIG. 2L, EPAM devices, 348and 349 are attached to vanes 345 mounted to a support structure 347 ina fluid conduit. When one of the pair of EPAM devices, 348 or 349lengthens, the other EPAM device contracts. The vanes 345 are deflectedupwards or downwards by the lengthening of one of the EPAM devices. Theposition of the vanes 345 in the fluid flow may be used to change thedirection of the fluid flowing over the vanes. The EPAM devices, 348 and349, and hence the direction of each of the vanes 345, may be controlledindependently. EPAM devices that bend in one or two planes where thebending is independently controlled in each plane are referred asunimorph and bimorph EPAM transducers. However, the present invention isnot limited to unimorph and bimorph EPAM transducers.

In 2L, EPAM devices, 350 are 351, are connected to a support structure347 and inserted into a fluid. The EPAM devices, 350 and 351, may berelatively flat and comprised of one or more EPAM polymer layers. TheEPAM polymers in the EPAM devices may be designed to deform (e.g., bend,twist and lengthen) in one or more directions in response to an appliedelectric field. The shape of the deflected EPAM devices and theirorientation relative to the flow may be used to alter the flowdirection. For instance, as shown in the FIG. 2M, the EPAM devices, 350and 351, may each deflect downwards to turn the flow in the conduitdownwards. In another embodiment, the EPAM devices, 350 and 351, maydeflect in opposite directions at some frequency to promote mixingand/or turbulence in the flow. In yet another embodiment, the EPAMdevices, 350 and 351, may deflect at some determined frequency to quietand dampen oscillations in the flow.

In FIG. 2N, a diaphragm array 353 for use as an EPAM flow control deviceis arranged around one or more portions or an entire circumference of afluid conduit. By deflecting the diaphragms in the diaphragm array 353in different patterns and with different frequencies, different wavepatterns may be introduced into the flow field. For instance, when thediaphragms are deflected parallel to the flow, transverse wave patterns,such as 354, may be added to the flow. As another example, when thediaphragms 353 are deflected in a pattern in a plane perpendicular tothe direction of the flow 306, such as around a circumference of acircular duct, vorticity in the fluid may be increased. By deflectingone diaphragm and letting it return and then repeating with an adjacentdiaphragm and so on around the circumference of the conduit, angularmomentum may be introduced into the flow.

The diaphragms may vary in height. At microscopic scales, an array ofdiaphragms may be used to alter surface roughness of a fluid conduit ora structure in an external flow. The properties of a flow boundary layernear a surface may be altered by changing the surface roughness viadeflections in a diaphragm array, such as 353. At larger scales,properties of an inviscid flow layer over a surface may be alter bydeflecting diaphragms to a height that is a significant fraction of theboundary layer height or greater than the boundary layer height at thelocation of each diaphragm.

In the present invention, a deflected height of the diaphragms may begreater than a height of a hemisphere. As an example, another device, anEPAM balloon valve 352 is shown in FIG. 2N. The EPAM balloon valve isattached to a support structure 347. The balloon valve may be deflectedso that it expands to block the fluid conduit. The expanded shape of theEPAM balloon valve 352 is nearly spherical and is indicated by thedashed lines.

FIGS. 2O-2R show example of a nozzle 415 with an EPAM nozzle body and avariable throat area controlled by an EPAM constrictor 419. Flow entersthe nozzle throat 417 via a feed line 420. The flow expands in the EPAMnozzle body 416 and exits the nozzle body 416 via a nozzle exit 418. TheEPAM nozzle body 416 may be designed to extend to lengthen the nozzlebody 416 by placing an electric field on an EPAM material comprising thenozzle body 416. The increased length of the nozzle body 416 may changean amount of expansion that occurs in the fluid as it travels in thenozzle body 416 to the exit 418. An increased expansion may reduce avelocity of the fluid as it exits the nozzle. In FIG. 2O, one example ofa deflected nozzle body is indicated by the dashed lines and another isindicated by the solid lines.

The EPAM constrictor 419 may be used to vary a throat area of the nozzle415 which may also change the expansion of the fluid in the nozzle. Achange in throat area of the nozzle may change fluid velocity profile atthe exit 418. In one embodiment, the EPAM valve 325 in FIG. 2G (withoutthe stop) may be used as a constrictor 419 to vary the throat area ofthe nozzle. Other types of constrictors may also be used (see FIGS. 3Kand 3L). For nozzles generating thrust, an optimum expansion for maximumthrust is related to the pressure at the nozzle exit. If the pressure atthe nozzle exit varies, then the nozzle geometry may be varied using theEPAM nozzle body 416 and EPAM constrictor 419 to optimize the nozzle 415to generate maximum thrust that corresponds to the pressure at thenozzle exit.

IN FIG. 2P, exit cross sections are shown for the two nozzle bodygeometries represented by the solid and dashed lines in FIG. 2O. Thefirst embodiment at a first deflected position has a circular crosssection 421. The second embodiment at a second deflected position has anovular cross section. When the nozzle is lengthened, the cross sectionalprofile may remain circular or change shapes. Many cross section shapesare possible and are not limited to an ovular cross section.

FIG. 2Q shows two cross sections, 423 and 424, for two deflectedpositions of the throat. The throat area 424 is smaller at the seconddeflected position than the throat area 423 at the first deflectedposition. The change in throat area is provided for illustrativepurposes only. In some embodiments (see FIG. 2R), the EPAM nozzle body416 may be deflected without a change in the throat area. The presentinvention is not limited to circular throat cross section. In someembodiments, the EPAM constrictor device may be unevenly constricted toproduce non-circular cross section at the nozzle throat 417.

In FIG. 2R, an embodiment is shown where the EPAM nozzle body 416 isdeflected to alter a direction of the flow as it exits the nozzle body.At its first deflection position (indicated by the solid lines), theflow exits the nozzle aligned in an axial direction through the centerof the nozzle. At its second deflection position (indicated by thedashed lines), the EPAM nozzle body is turned downwards to direct theflow exiting the nozzle in a downward direction. To turn the nozzle bodydownward, a greater electric field may be applied to the EPAM polymer ontop of the EPAM nozzle body versus on the bottom of the EPAM nozzlebody. The additional electric field may cause the top of the nozzle bodyto lengthen more than the bottom of the nozzle body and hence turn thenozzle body downwards.

This capability may provide an additional degree of control for an EPAMnozzle that is not easily obtained with a conventional nozzle. Aconventional nozzle would require an additional mechanism to deflect thenozzle. An EPAM nozzle only requires a compatible electrode pattern andcharge control mechanism which are already components of an EPAM device.

In FIGS. 3A-M a number of valve designs employing EPAM polymer elementsare shown. Examples of valve designs shown in the figures include adiaphragm valve (FIG. 3A), a gate valve (FIGS. 3B and 3C), a needlevalve (FIG. 3D), a slot valve (FIGS. 3F and 3G), rotary valves withmultiple ports (FIGS. 3G-3J), a pinch valve (FIGS. 3K and 3M) andinput/exhaust valves for a combustion chamber (FIG. 3M). The presentinvention is not limited to these types of valves as the EPAM polymersof the present invention may be applied to many other types of valvedesigns not shown.

As the term is used herein, a “valve” is one embodiment of a flowcontrol device. A valve, as well as a flow control device, refers to adevice that regulates, affects or controls fluidic communication ofgases, liquids and/or loose particles through one or more structures.For example, a valve may control the flow of gases into a chamber, suchas the combustion chamber of an internal combustion engine; or from aconduit, such as an air inlet port leading to the combustion chamber.One or more exhaust valves actuated by an EP transducer may also bedisposed on the outlet of the chamber. Alternately, a valve may bedisposed in a conduit (e.g., a pipe) to regulate pressure betweenopposite sides of the valve and thereby regulate pressure downstreamfrom the valve.

Valves and flow control devices as described herein comprise one or moreelectroactive polymer (EPAM) transducers. In one embodiment, the EPAMtransducer is used as to actuate the valve, or provide mechanical energyto regulate fluidic communication of gases, liquids and/or looseparticles through the valve. Linear EPAM transducers are particularlywell suited to provide on/off control of a valve as well as incrementaland precise levels of control (proportional control). Given the fastresponse time of an EPAM transducer, valves of the present invention arethus well suited for applications requiring time sensitive fluidicregulation. In some cases, the EPAM transducer may not directly contactthe fluid (e.g., see FIG. 3M). For example, a linear EPAM transducer maybe coupled to a sealed fluid interface that acts upon the fluid, such asa gate within a conduit having one or more moving parts affected byactuation of the EPAM transducer (see FIGS. 3B and 3C). In this case,the EPAM transducer actuates the valve using the fluid interface. Inother embodiments, the EPAM transducer may include a surface thatcontacts the fluid, such as a diaphragm EPAM transducer disposed in aconduit to regulate the flow of a fluid over a surface of the diaphragm(see FIG. 3A). Actuation of the diaphragm EPAM transducer may decreasethe cross sectional area of the conduit to reduce a fluid flow rate, orclose the conduit completely, to block fluid flow in the conduit.

In FIG. 3A, a diaphragm valve design is shown. A traditional diaphragmvalve closes by using a flexible diaphragm attached to a compressor. Thecompressor may be used to press the diaphragm against a weir, which is araised flat surface in a flow stream, or into a valve seat. When thediaphragm is pressed into the weir or the valve seat, a seal is formedand the flow is cut off.

In FIG. 3A, a design of a EPAM diaphragm valve 360 is shown. An EPAMdiaphragm 360 is attached to a support structure 347. A bias mechanism364, such as a spring, a foam cut-off or gas pressure, may be used toprovide the diaphragm with an outward deflection. The support structureitself may be permeable to the flow, and if the pressure of the pumpedfluid is higher on the valve side than on the exit side (common inpumped fluid applications where pressure is higher upstream than downstream), then the pressure differential of the pumped flow itself mayserve as a bias mechanism. In a first deflected position (indicated bythe solid line), a fluid may flow through the valve 360 and through thevalve seat 363, which may include an orifice. An electric field may beapplied to EPAM polymer in the diaphragm 363 to deflect the diaphragm toa second position in contact with the valve seat 363 and covering theorifice. In the second position, flow through the valve is blocked.

In another embodiment, the EPAM diaphragm 363 may be deflected to pressagainst a weir in a fluid conduit. To improve sealing, the EPAMdiaphragm may have additional layers of material on the side of thediaphragm in contact with the valve seat 363. An advantage of the valve360 is that the functions of the compressor and diaphragm are combined.In a traditional diaphragm valve, a separate compressor element istypically required.

In FIGS. 3B and 3C, a gate valve 365 with EPAM actuators used to controla valve cover 366 (i.e., gate) are shown. In a gate valve, the flow maybe controlled by a flat face, vertical disc or gate that slides downthrough the valve to block the flow. In FIG. 3B, the gate valve 365 isshown in an open position. Two EPAM actuators, 367 and 368, are shownattached to a valve cover 366. Alternately, 367 and 368 may be two sides(in cross section) of a single EPAM actuator such as a rolled EPAMactuator. The EPAM actuators are configured such that applying anelectric field causes an EPAM polymer in the actuators to lengthen andpush the valve cover 366 away from the valve seat 363. A forcemechanism, such as a spring or a magnetic device, is configured to pushthe valve cover 366 towards the valve seating and against the valve seat363. When the electric field to the EPAM actuators is reduced or turnedoff, a length of the EPAM polymers is shortened and the valve cover 366closes over the valve seat to block the flow.

The valve 365 may be capable of being calibrated. In the calibrationprocedure, the electric field applied to EPAM polymers in the actuators367 and 368 may be adjusted according to a force applied by the forcemechanism 364 to ensure a proper closure of the valve 365 is obtained.The calibration process may be useful when the force applied by theforce mechanism changes with time. For instance, a force applied by aspring may change with time after repeated stretching and contracting ofthe spring.

The diaphragm valve 360 and gate valve in 365 may also be used ascontrol valves. A control valve is designed to ensure accurateproportioning control of fluid through the valve. The control valve mayautomatically vary the rate of flow through the valve based upon signalsit receives from sensing devices in a continuous process. Most types ofvalves, using either linear or rotary motion, may be used as controlvalves by the addition of power actuators, positioners, sensors andother accessories. As an example, in FIG. 3A, to control the flow invalve 360, a flow rate sensor and/or a sensor for detecting the positionof the diaphragm 364 may be used. The EPAM itself can be used as asensor which is described below in the section titled sensing. Thediaphragm may be deflected to different positions depending on thedetermined and desired flow rate through the valve.

In FIG. 3D, an example of a needle valve 370 is shown. Needle valves arevolume control valves that are often used to restrict the flow of afluid in a small line. The fluid 371 passes through an orifice that is aseat 363 for the valve cover 366. In an in-line valve, the fluid may bepassed through a 90 degree turn that includes the needle valve. Thevalve cover 366 is typically conically shaped. By positioning the valvecover 366 relative to the seat 363, the size of the orifice may bechanged.

In FIG. 3D, an EPAM actuator 372 is attached to a support structure 347.When an electric field is applied to the EPAM polymer in the actuator,the EPAM polymer lengthens and the valve cover is pushed towards thevalve seat 363 to change the size of the orifice allowing fluid flow.Two forces mechanisms, which may be springs, apply a force in theopposite direction of the force transferred to the valve seat 363 by theEPAM polymer. When the electric field on the EPAM polymer is reduced,the force mechanisms may pull the valve cover 366 away from the seat363.

In FIGS. 3E and 3F an example of a slot valve 375 is shown. The slotvalve includes a channel that is designed to be aligned or unalignedwith an input port and an output port. When the slot valve is alignedwith the input port and the output port, fluid may move through thechannel in a slot cover from the input port to the output port. When theslot valve is unaligned, the input port is blocked and the fluid flowthrough the slot is blocked.

In FIG. 3E, the slot valve is shown in the aligned position. An EPAMactuator 377 anchored to a support structure is actuated to push theslot cover 376 into alignment with the input and output ports. The slotcover 376 may reside in a slot, which guides its motion. The slot coveris attached to a force mechanism 364 that is attached to a supportstructure 347. The force mechanism 364 provides a force in the directionopposite to the force applied by the EPAM actuator 377 when it isactuated. When the electric field applied to the EPAM polymer in theactuator 377 is reduced or turned off, the force mechanism 364 pushesthe slot cover into an unaligned position blocking the input port andthe flow through the channel in the slot cover 376. The unalignedposition of the slot valve 375 is shown in FIG. 3F.

In FIGS. 3G-3J, some examples of rotary valves are shown. The valvesinclude multiple ports. Traditional examples of rotary valves includeplug valves or ball valves. In these types of valves, a plug or ballwith a channel is rotated to line up in a flow path or line up to blockthe flow path. Typically, a rotation in the valve, such as a 90 degreeturn is required to align or unalign the channel with a flow path.Because of the required rotation to turn the valves on and off, thesevalves are referred to as rotary valves.

In FIGS. 3H and 3I, one embodiment of a rotary multi-port valve 380 isshown. The multi-port rotary valve comprises a partially hollow EPAMroll actuator 381 with a fluid conduit 382 that runs through the center.A port 383 through the side of the EPAM 381 connects to the fluidconduit 382. The port is designed to connect to one of a plurality offeed lines 384.

The EPAM roll 381 is designed to actuate along a curved path. The valve380 may include guides that help to guide the EPAM roll along a set pathas it actuates. In FIG. 3G, when the EPAM roll is not actuated tolengthen the roll, the port 383 does not align with any of the feedlines 384. For instance, the EPAM roll 381 may be deflected to expand indiameter and block the feed lines. Further, the side of the EPAM roll381 may be used to block the feed lines 384. In other embodiment, theport 383 may include a mechanism that opens and mates with a valve onthe feed line. In 3H, when the EPAM roll 381 is actuated to lengthenalong a curved path, the port 383 rotates along the path to align with amiddle of three feed lines. In this position, fluid may enter theconduit from the middle feed line and flow through the fluid conduit 382in the center of the EPAM roll. In this deflected position, the openingto the other two feed lines may be blocked by the side of the EPAM rollor may be closed using another mechanism, such as a valve.

In FIGS. 3I and 3J, another embodiment of an EPAM multi-port valve 390is shown. In this embodiment, two fluid conduits run through an EPAMroll 393. Two ports, 391 and 392, each respectively on a front end ofthe two fluid conduits, are designed for connection to two feed lines ata fixed position. A view of the multi-port rotary valve 390 from theside with the two ports, 391 and 392, is shown in FIG. 3I.

A cross-section of the EPAM roll 393 is show in FIG. 3J. The EPAM roll393 is designed to rotate torsionally to align ports 396 and 397opposite to ports 391 and 392 with two feed lines 385 and 386. When port396 is aligned with port 385, a fluid may travel through a first fluidconduit in the EPAM roll 393 to port 392. Similarly, when port 397 isaligned with port 386, fluid may flow through a second conduit in theEPAM roll 383 to port 391. The first and the second fluid conduits areat different heights in the EPAM roll. The EPAM roll may be designedsuch that an upper portion of the roll rotates torsionally independentlyof a lower portion of the EPAM roll. Thus, ports 396 and 397 may beconnected or disconnected from ports 385 and 386 independently.

In FIGS. 3K and 3L, an embodiment of a pinch valve is shown. A pinchvalve seals by squeezing on a flexible conduit, such as a rubber tube,that can be pinched to shut off the fluid flow in the conduit. Pinchvalves are often used for slurries or liquids with large amounts ofsuspended solids. In FIG. 3K, a cross section of an EPAM constrictordevice 400 around a flexible fluid conduit 402 is shown. The EPAMconstrictor device includes a plurality of EPAM actuators 401. The EPAMactuators include an EPAM polymer that is designed to deflect toward acenter of the fluid under application of an electric field.

The EPAM actuators push towards the center of the fluid conduit to pinchit off and decrease a diameter 303. In FIG. 3L, a section of the fluidconduit 402 from the side is shown. The dashed lines indicate deflectedpositions of both the constrictor device 400 and the fluid conduit 402.As the deflection of the constrictor device increases, the diameter 403in the conduit 402 decreases. In one embodiment, the constrictor device400 may be used as a cuff or sleeve around a human limb, such as an armor a leg, to pinch off a blood flow in vessels in the arm or the legwhen the constrictor is deflected. In another example, the cuff orsleeve may be used around a human organ to constrict blood flow in thehuman organ. A few other types of valves not shown that may be used asflow EPAM flow control devices include but are not limited to 1) checkvalves designed to prevent backflow, 2) pressure relief valves designedto provide protection from over-pressure and 3) buttery fly valves thatcontrol the flow by using a circular disc or vane with its pivot axis atright angles to the direction of the flow.

A simple diaphragm by itself may function as a flow control devicesusing variable permeability (configuration not shown). For example, iffluid under pressure is on one side of an EPAM diaphragm, and the EPAMdiaphragm is permeable to the fluid, then actuating the EPAM diaphragmto make it expand in area and contract in thickness will increase itspermeability and allow the pressurized fluid to diffuse through the EPAMdiaphragm at greater rates. Many fluids such as gasses and smallerliquid molecules under pressure can diffuse through EPAM elastomers andEPAM electrodes.

In one embodiment, an EPAM actuator is used to actuate the intake 413and exhaust valves 412 to the combustion chamber 414 in an internalcombustion engine using a roll-type electroactive polymer transducer410. This embodiment is shown in FIG. 3M. The EPAM actuators are mountedto the cylinder head 411 via support members 415 bolted to the cylinderhead. The EPAM actuators 410 may control the opening and closing of theintake and exhaust valves.

EPAM transducers overcome many of the limitations of conventionalactuation technologies and enable the actuation of engine valvesindividually for variable timing and lift. EPAM transducers have linearforce characteristics, inherent proportional control (for variablelift), high efficiency, low noise, good packaging flexibility, and the“soft landing” ability. For example, solenoids tend to snap shut at theend of their travel, resulting in noise and accelerated valve wear; EPAMtransducers can provide “soft landing” to reduce noise and wear. EPAMtransducers also provide higher power-to-weight ratio than solenoids orhydraulics.

By using EPAM transducers to actuate the intake/exhaust valves, valvetiming and lift can be better matched to the engine requirements atdifferent speeds, and a broader range of power and economy can beachieved from the engine. The use of EPAM transducers eliminates theneed for the camshaft and related drive hardware, and enables infinitevariable valving for camless engines. Furthermore, EPAM transducers canbe used to achieve individual cylinder control in an internal combustionengine which is not possible today. Individual cylinders can be enabledor disabled on demand by either actuating or not actuating theintake/exhaust valves. For example, an eight-cylinder engine can run asa four- or six-cylinder as needed. This greatly increase the flexibilityof engine power output and fuel economy.

The control of an EPAM actuated valves of the present invention may bepulse-width modulated (PWM), where the valve is open for a certainpercentage of each cycle of a high frequency signal. The open percentage(or duty cycle) is varied with the flow requirement. The valve can alsobe proportionally controlled where the position of the valve iscontrolled and varied according to the flow requirements. Thisproportional control is difficult with the conventional solenoidscurrently used. The EPAM actuated valve can also be frequency modulated(FM). The frequency of actuation and spring rates can be designed tooperate at resonance, which can reduce the power requirements of theactuator. Flow control would be done by varying the frequency away fromthe resonance frequency.

There are a wide variety of applications of an EPAM actuated valve forcontrolling fluid flow and/or regulating pressure. EPAM transducers havethe advantages of reduced weight, costs, and complexity and increasedoperating flexibility compared to conventional flow control systems. Inan automobile, an EPAM actuated valve can be used for fuel injectioncontrol, air intake control (throttle position), cooling system andemission control. For example, the EPAM actuated valve described hereincan be used as the canister purge valve (CPV) in internal combustionengines. The CPV controls flow between a fuel vapor canister atatmospheric pressure and the air intake system of an internal combustionengine at partial vacuum. The EP actuated valve enables proportionalcontrol of fuel vapor flow, which is difficult to achieve with solenoidtypes of valves. As another example, the EPAM actuated valve can replacethe conventional pneumatically actuated valve system for controllingflow of exhaust to the muffler. In the embodiments described herein andin many other applications, the EPAM actuated valve can be readilyintegrated into their surrounding structures.

Electroactive Polymer Devices Transducers

FIGS. 4A-2E show a rolled electroactive polymer device 20 in accordancewith one embodiment of the present invention. The rolled electroactivepolymer device may be used for actuation of an EPAM flow control device(e.g., see FIG. 2C-2F, 2L or 3G-3I) and may also act as part of a fluidconduit or other types of structures immersed in an external or internalflowfield. The rolled electroactive polymer devices may provide linearand/or rotational/torsional motion for operating the EPAM flow controldevice. FIG. 4A illustrates a side view of device 20. FIG. 4Billustrates an axial view of device 20 from the top end. FIG. 4Cillustrates an axial view of device 20 taken through cross section A-A.FIG. 4D illustrates components of device 20 before rolling. Device 20comprises a rolled electroactive polymer 22, spring 24, end pieces 27and 28, and various fabrication components used to hold device 20together.

As illustrated in FIG. 4C, electroactive polymer 22 is rolled. In oneembodiment, a rolled electroactive polymer refers to an electroactivepolymer with, or without electrodes, wrapped round and round onto itself(e.g., like a poster) or wrapped around another object (e.g., spring24). The polymer may be wound repeatedly and at the very least comprisesan outer layer portion of the polymer overlapping at least an innerlayer portion of the polymer. In one embodiment, a rolled electroactivepolymer refers to a spirally wound electroactive polymer wrapped aroundan object or center. As the term is used herein, rolled is independentof how the polymer achieves its rolled configuration.

As illustrated by FIGS. 4C and 4D, electroactive polymer 22 is rolledaround the outside of spring 24. Spring 24 provides a force that strainsat least a portion of polymer 22. The top end 24 a of spring 24 isattached to rigid endpiece 27. Likewise, the bottom end 24 b of spring24 is attached to rigid endpiece 28. The top edge 22 a of polymer 22(FIG. 4D) is wound about endpiece 27 and attached thereto using asuitable adhesive. The bottom edge 22 b of polymer 22 is wound aboutendpiece 28 and attached thereto using an adhesive. Thus, the top end 24a of spring 24 is operably coupled to the top edge 22 a of polymer 22 inthat deflection of top end 24 a corresponds to deflection of the topedge 22 a of polymer 22. Likewise, the bottom end 24 b of spring 24 isoperably coupled to the bottom edge 22 b of polymer 22 and deflectionbottom end 24 b corresponds to deflection of the bottom edge 22 b ofpolymer 22. Polymer 22 and spring 24 are capable of deflection betweentheir respective bottom top portions.

As mentioned above, many electroactive polymers perform better whenprestrained. For example, some polymers exhibit a higher breakdownelectric field strength, electrically actuated strain, and energydensity when prestrained. Spring 24 of device 20 provides forces thatresult in both circumferential and axial prestrain onto polymer 22.

Spring 24 is a compression spring that provides an outward force inopposing axial directions (FIG. 4A) that axially stretches polymer 22and strains polymer 22 in an axial direction. Thus, spring 24 holdspolymer 22 in tension in axial direction 35. In one embodiment, polymer22 has an axial prestrain in direction 35 from about 50 to about 300percent. As will be described in further detail below for fabrication,device 20 may be fabricated by rolling a prestrained electroactivepolymer film around spring 24 while it the spring is compressed. Oncereleased, spring 24 holds the polymer 22 in tensile strain to achieveaxial prestrain.

Spring 24 also maintains circumferential prestrain on polymer 22. Theprestrain may be established in polymer 22 longitudinally in direction33 (FIG. 4D) before the polymer is rolled about spring 24. Techniques toestablish prestrain in this direction during fabrication will bedescribed in greater detail below. Fixing or securing the polymer afterrolling, along with the substantially constant outer dimensions forspring 24, maintains the circumferential prestrain about spring 24. Inone embodiment, polymer 22 has a circumferential prestrain from about100 to about 500 percent. In many cases, spring 24 provides forces thatresult in anisotropic prestrain on polymer 22.

End pieces 27 and 28 are attached to opposite ends of rolledelectroactive polymer 22 and spring 24. FIG. 4E illustrates a side viewof end piece 27 in accordance with one embodiment of the presentinvention. Endpiece 27 is a circular structure that comprises an outerflange 27 a, an interface portion 27 b, and an inner hole 27 c.Interface portion 27 b preferably has the same outer diameter as spring24. The edges of interface portion 27 b may also be rounded to preventpolymer damage. Inner hole 27 c is circular and passes through thecenter of endpiece 27, from the top end to the bottom outer end thatincludes outer flange 27 a. In a specific embodiment, endpiece 27comprises aluminum, magnesium or another machine metal. Inner hole 27 cis defined by a hole machined or similarly fabricated within endpiece27. In a specific embodiment, endpiece 27 comprises ½ inch end caps witha ⅜ inch inner hole 27 c.

In one embodiment, polymer 22 does not extend all the way to outerflange 27 a and a gap 29 is left between the outer portion edge ofpolymer 22 and the inside surface of outer flange 27 a. As will bedescribed in further detail below, an adhesive or glue may be added tothe rolled electroactive polymer device to maintain its rolledconfiguration. Gap 29 provides a dedicated space on endpiece 27 for anadhesive or glue than the buildup to the outer diameter of the rolleddevice and fix to all polymer layers in the roll to endpiece 27. In aspecific embodiment, gap 29 is between about 0 mm and about 5 mm.

The portions of electroactive polymer 22 and spring 24 between endpieces 27 and 28 may be considered active to their functional purposes.Thus, end pieces 27 and 28 define an active region 32 of device 20 (FIG.4A). End pieces 27 and 28 provide a common structure for attachment withspring 24 and with polymer 22. In addition, each end piece 27 and 28permits external mechanical and detachable coupling to device 20. Forexample, device 20 may be employed in a robotic application whereendpiece 27 is attached to an upstream link in a robot and endpiece 28is attached to a downstream link in the robot. Actuation ofelectroactive polymer 22 then moves the downstream link relative to theupstream link as determined by the degree of freedom between the twolinks (e.g., rotation of link 2 about a pin joint on link 1).

In a specific embodiment, inner hole 27 c comprises an internal threadcapable of threaded interface with a threaded member, such as a screw orthreaded bolt. The internal thread permits detachable mechanicalattachment to one end of device 20. For example, a screw may be threadedinto the internal thread within end piece 27 for external attachment toa robotic element. For detachable mechanical attachment internal todevice 20, a nut or bolt to be threaded into each end piece 27 and 28and pass through the axial core of spring 24, thereby fixing the two endpieces 27 and 28 to each other. This allows device 20 to be held in anystate of deflection, such as a fully compressed state useful duringrolling. This may also be useful during storage of device 20 so thatpolymer 22 is not strained in storage.

In one embodiment, a stiff member or linear guide 30 is disposed withinthe spring core of spring 24. Since the polymer 22 in spring 24 issubstantially compliant between end pieces 27 and 28, device 20 allowsfor both axial deflection along direction 35 and bending of polymer 22and spring 24 away from its linear axis (the axis passing through thecenter of spring 24). In some embodiments, only axial deflection isdesired. Linear guide 30 prevents bending of device 20 between endpieces 27 and 28 about the linear axis. Preferably, linear guide 30 doesnot interfere with the axial deflection of device 20. For example,linear guide 30 preferably does not introduce frictional resistancebetween itself and any portion of spring 24. With linear guide 30, orany other suitable constraint that prevents motion outside of axialdirection 35, device 20 may act as a linear actuator or generator withoutput strictly in direction 35. Linear guide 30 may be comprised of anysuitably stiff material such as wood, plastic, metal, etc.

Polymer 22 is wound repeatedly about spring 22. For single electroactivepolymer layer construction, a rolled electroactive polymer of thepresent invention may comprise between about 2 and about 200 layers. Inthis case, a layer refers to the number of polymer films or sheetsencountered in a radial cross-section of a rolled polymer. In somecases, a rolled polymer comprises between about 5 and about 100 layers.In a specific embodiment, a rolled electroactive polymer comprisesbetween about 15 and about 50 layers.

In another embodiment, a rolled electroactive polymer employs amultilayer structure. The multilayer structure comprises multiplepolymer layers disposed on each other before rolling or winding. Forexample, a second electroactive polymer layer, without electrodespatterned thereon, may be disposed on an electroactive polymer havingelectrodes patterned on both sides. The electrode immediately betweenthe two polymers services both polymer surfaces in immediate contact.After rolling, the electrode on the bottom side of the electrodedpolymer then contacts the top side of the non-electroded polymer. Inthis manner, the second electroactive polymer with no electrodespatterned thereon uses the two electrodes on the first electrodedpolymer.

Other multilayer constructions are possible. For example, a multilayerconstruction may comprise any even number of polymer layers in which theodd number polymer layers are electroded and the even number polymerlayers are not. The upper surface of the top non-electroded polymer thenrelies on the electrode on the bottom of the stack after rolling.Multilayer constructions having 2, 4, 6, 8, etc., are possible thistechnique. In some cases, the number of layers used in a multilayerconstruction may be limited by the dimensions of the roll and thicknessof polymer layers. As the roll radius decreases, the number ofpermissible layers typically decrease is well. Regardless of the numberof layers used, the rolled transducer is configured such that a givenpolarity electrode does not touch an electrode of opposite polarity. Inone embodiment, multiple layers are each individually electroded andevery other polymer layer is flipped before rolling such that electrodesin contact each other after rolling are of a similar voltage orpolarity.

The multilayer polymer stack may also comprise more than one type ofpolymer For example, one or more layers of a second polymer may be usedto modify the elasticity or stiffness of the rolled electroactivepolymer layers. This polymer may or may not be active in thecharging/discharging during the actuation. When a non-active polymerlayer is employed, the number of polymer layers may be odd. The secondpolymer may also be another type of electroactive polymer that variesthe performance of the rolled product.

In one embodiment, the outermost layer of a rolled electroactive polymerdoes not comprise an electrode disposed thereon. This may be done toprovide a layer of mechanical protection, or to electrically isolateelectrodes on the next inner layer. For example, inner and outer layersand surface coating may be selected to provide fluid compatibility aspreviously described. The multiple layer characteristics described abovemay also be applied non-rolled electroactive polymers, such as EPAMdiaphragms previously described.

Device 20 provides a compact electroactive polymer device structure andimproves overall electroactive polymer device performance overconventional electroactive polymer devices. For example, the multilayerstructure of device 20 modulates the overall spring constant of thedevice relative to each of the individual polymer layers. In addition,the increased stiffness of the device achieved via spring 24 increasesthe stiffness of device 20 and allows for faster response in actuation,if desired.

In a specific embodiment, spring 24 is a compression spring such ascatalog number 11422 as provided by Century Spring of Los Angeles,Calif. This spring is characterized by a spring force of 0.91 lb/inchand dimensions of 4.38 inch free length, 1.17 inch solid length, 0.360inch outside diameter, 0.3 inch inside diameter. In this case, rolledelectroactive polymer device 20 has a height 36 from about 5 to about 7cm, a diameter 37 of about 0.8 to about 1.2 cm, and an active regionbetween end pieces of about 4 to about 5 cm. The polymer ischaracterized by a circumferential prestrain from about 300 to about 500percent and axial prestrain (including force contributions by spring 24)from about 150 to about 250 percent.

Although device 20 is illustrated with a single spring 24 disposedinternal to the rolled polymer, it is understood that additionalstructures such as another spring external to the polymer may also beused to provide strain and prestrain forces. These external structuresmay be attached to device 20 using end pieces 27 and 28 for example.

FIG. 4F illustrates a bending transducer 150 for providing variablestiffness based on structural changes in accordance with one embodimentof the present invention. In this case, transducer 150 varies andcontrols stiffness in one direction using polymer deflection in anotherdirection. In one embodiment, this device may be used a vane in a fluidflow as described with respect to FIGS. 2K and 2L. Transducer 150includes a polymer 151 fixed at one end by a rigid support 152. Attachedto polymer 151 is a flexible thin material 153 such as polyimide ormylar using an adhesive layer, for example. The flexible thin material153 has a modulus of elasticity greater than polymer 151. The differencein modulus of elasticity for the top and bottom sides 156 and 157 oftransducer 150 causes the transducer to bend upon actuation. Electrodes154 and 155 are attached to the opposite sides of the polymer 151 toprovide electrical communication between polymer 151 and controlelectronics used to control transducer 150 deflection. Transducer 150 isnot planar but rather has a slight curvature about axis 160 as shown.Direction 160 is defined as rotation or bending about a line extendingaxially from rigid support 152 through polymer 151. This curvature makestransducer 150 stiff in response to forces applied to the tip along anyof the directions indicated by the arrows 161. In place of, or inaddiction to forces, torques may be applied to the transducer. Thesetorques may be applied about the axis indicated by the arrows ofdirections 161 a and 161 b.

FIG. 4G illustrates transducer 150 with a deflection in direction 161 bthat is caused by the application of a voltage to he electrodes 154 and155. The voltage is applied to allow the bending forces to overcome theresistance presented by the curvature in the unactuated state.Effectively, the transducer 152 bends with a kink caused by the initialcurvature. In this state, the stiffness in response to the forces ortorques indicated by directions 161 is much less.

A mechanical interface may be attached to the distal portion 159 oftransducer 150. Alternately, mechanical attachment may be made to theflexible thin material 153 to allow transducer 150 implementation in amechanical device. For example, transducer 150 is well suited for use inapplications such as lightweight space structures where folding of thestructure, so that it can be stowed and deployed, is useful. In thisexample, the stiff condition of individual transducers (which form ribsin the structure) occurs when the structure is deployed. To allow forstowing, the transducers are actuated and the ribs may be bent. Inanother application, the transducers form ribs in the sidewall ofpneumatic tires. In this application, the change in the stiffness of theribs can affect the stiffness of the tires and thus the resultanthandling of the vehicle that uses the tires. Similarly, the device maybe implemented in a shoe and the change in stiffness of the ribs canaffect the stiffness of the shoe.

Transducer 150 provides one example where actuation of an electroactivepolymer causes low-energy changes in configuration or shape that affectsstiffness of a device. Using this technique, it is indeed possible tovary stiffness using transducer 150 at greater levels than directmechanical or electrical energy control. In another embodiment,deflection of an electroactive polymer transducer directly contributesto the changing stiffness of a device that the transducer is configuredwithin.

FIG. 4H illustrates a bow device 200 suitable for providing variablestiffness in accordance with another embodiment of the presentinvention. Bow device 200 is a planar mechanism comprising a flexibleframe 202 attached to a polymer 206. The frame 202 includes six rigidmembers 204 pivotally connected at joints 205. The members 204 andjoints 205 couple polymer deflection in a planar direction 208 intomechanical output in a perpendicular planar direction 210. Bow device200 is in a resting position as shown in FIG. 4H. Attached to opposite(top and bottom) surfaces of the polymer 206 are electrodes 207 (bottomelectrode on bottom side of polymer 206 not shown) to provide electricalcommunication with polymer 206. FIG. 4I illustrates bow device 200 afteractuation.

In the resting position of FIG. 4H, rigid members 204 provide a largestiffness to forces 209 in direction 208, according to their materialstiffness. However, for the position of bow device 200 as shown in FIG.4I, the stiffness in direction 208 is based on the compliance of polymer202 and any rotational elastic resistance provided by joints 205. Thus,control electronics in electrical communication with electrodes 207 maybe used to apply an electrical state that produces deflection forpolymer 206 as shown in FIG. 4H, and its corresponding high stiffness,and an electrical state that produces deflection for polymer 206 asshown in FIG. 4I, and its corresponding low stiffness. In this, simpleon/off control may be used to provide a large stiffness change usingdevice 200.

In addition to stiffness variation achieved by varying the configurationof rigid members in device 200, stiffness for the position of FIG. 4Imay additionally be varied using one of the open or closed loopstiffness techniques described in detail in commonly owned U.S. Pat. No.6,882,086, by Kornbluh et al and titled “Variable StiffnessElectroactive Polymers,” which is incorporated herein in its entiretyand for all purposes.

Multiple Active Areas

In some cases, electrodes cover a limited portion of an electroactivepolymer relative to the total area of the polymer. This may be done toprevent electrical breakdown around the edge of a polymer, to allow forpolymer portions to facilitate a rolled construction (e.g., an outsidepolymer barrier layer), to provide multifunctionality, or to achievecustomized deflections for one or more portions of the polymer. As theterm is used herein, an active area is defined as a portion of atransducer comprising a portion of an electroactive polymer and one ormore electrodes that provide or receive electrical energy to or from theportion. The active area may be used for any of the functions describedbelow. For actuation, the active area includes a portion of polymerhaving sufficient electrostatic force to enable deflection of theportion. For generation or sensing, the active area includes a portionof polymer having sufficient deflection to enable a change inelectrostatic energy. A polymer of the present invention may havemultiple active areas.

In accordance with the present invention, the term “monolithic” is usedherein to refer to electroactive polymers and transducers comprising aplurality of active areas on a single polymer. FIG. 4J illustrates amonolithic transducer 150 comprising a plurality of active areas on asingle polymer 151 in accordance with one embodiment of the presentinvention. The monolithic transducer 150 converts between electricalenergy and mechanical energy. The monolithic transducer 150 comprises anelectroactive polymer 151 having two active areas 152 a and 152 b.Polymer 151 may be held in place using, for example, a rigid frame (notshown) attached at the edges of the polymer. Coupled to active areas 152a and 152 b are wires 153 that allow electrical communication betweenactive areas 152 a and 152 b and allow electrical communication withcommunication electronics 155.

Active area 152 a has top and bottom electrodes 154 a and 154 b that areattached to polymer 151 on its top and bottom surfaces 151 c and 151 d,respectively. Electrodes 154 a and 154 b provide or receive electricalenergy across a portion 151 a of the polymer 151. Portion 151 a maydeflect with a change in electric field provided by the electrodes 154 aand 154 b. For actuation, portion 151 a comprises the polymer 151between the electrodes 154 a and 154 b and any other portions of thepolymer 151 having sufficient electrostatic force to enable deflectionupon application of voltages using the electrodes 154 a and 154 b. Whenactive area 152 a is used as a generator to convert from electricalenergy to mechanical energy, deflection of the portion 151 a causes achange in electric field in the portion 151 a that is received as achange in voltage difference by the electrodes 154 a and 154 b.

Active area 152 b has top and bottom electrodes 156 a and 156 b that areattached to the polymer 151 on its top and bottom surfaces 151 c and 151d, respectively. Electrodes 156 a and 156 b provide or receiveelectrical energy across a portion 151 b of the polymer 151. Portion 151b may deflect with a change in electric field provided by the electrodes156 a and 156 b. For actuation, portion 151 b comprises the polymer 151between the electrodes 156 a and 156 b and any other portions of thepolymer 151 having sufficient stress induced by the electrostatic forceto enable deflection upon application of voltages using the electrodes156 a and 156 b. When active area 152 b is used as a generator toconvert from electrical energy to mechanical energy, deflection of theportion 151 b causes a change in electric field in the portion 151 bthat is received as a change in voltage difference by the electrodes 156a and 156 b.

Active areas for an electroactive polymer may be easily patterned andconfigured using conventional electroactive polymer electrodefabrication techniques. Multiple active area polymers and transducersare further described in Ser. No. 09/779,203, which is incorporatedherein by reference for all purposes. Given the ability to pattern andindependently control multiple active areas allows rolled transducers ofthe present invention to be employed in many new applications; as wellas employed in existing applications in new ways.

FIG. 4K illustrates a monolithic transducer 170 comprising a pluralityof active areas on a single polymer 172, before rolling, in accordancewith one embodiment of the present invention. In present invention, themonolithic transducer 170 may be utilized in a rolled or unrolledconfiguration. Transducer 170 comprises individual electrodes 174 on thefacing polymer side 177. The opposite side of polymer 172 (not shown)may include individual electrodes that correspond in location toelectrodes 174, or may include a common electrode that spans in area andservices multiple or all electrodes 174 and simplifies electricalcommunication. Active areas 176 then comprise portions of polymer 172between each individual electrode 174 and the electrode on the oppositeside of polymer 172, as determined by the mode of operation of theactive area. For actuation for example, active area 176 a for electrode174 a includes a portion of polymer 172 having sufficient electrostaticforce to enable deflection of the portion, as described above.

Active areas 176 on transducer 170 may be configured for one or morefunctions. In one embodiment, all active areas 176 are all configuredfor actuation. In another embodiment suitable for use with roboticapplications, one or two active areas 176 are configured for sensingwhile the remaining active areas 176 are configured for actuation. Inthis manner, a rolled electroactive polymer device using transducer 170is capable of both actuation and sensing. Any active areas designatedfor sensing may each include dedicated wiring to sensing electronics, asdescribed below.

At shown, electrodes 174 a-d each include a wire 175 a-d attachedthereto that provides dedicated external electrical communication andpermits individual control for each active area 176 a-d. Electrodes 174e-i are all electrical communication with common electrode 177 and wire179 that provides common electrical communication with active areas 176e-i. Common electrode 177 simplifies electrical communication withmultiple active areas of a rolled electroactive polymer that areemployed to operate in a similar manner. In one embodiment, commonelectrode 177 comprises aluminum foil disposed on polymer 172 beforerolling. In one embodiment, common electrode 177 is a patternedelectrode of similar material to that used for electrodes 174 a-i, e.g.,carbon grease.

For example, a set of active areas may be employed for one or more ofactuation, generation, sensing, changing the stiffness and/or damping,or a combination thereof. Suitable electrical control also allows asingle active area to be used for more than one function. For example,active area 174 a may be used for actuation and variable stiffnesscontrol of a fluid conduit. The same active area may also be used forgeneration to produce electrical energy based on motion of the fluidconduit. Suitable electronics for each of these functions are describedin further detail below. Active area 174 b may also be flexibly used foractuation, generation, sensing, changing stiffness, or a combinationthereof. Energy generated by one active area may be provided to anotheractive area, if desired by an application. Thus, rolled polymers andtransducers of the present invention may include active areas used as anactuator to convert from electrical to mechanical energy, a generator toconvert from mechanical to electrical energy, a sensor that detects aparameter, or a variable stiffness and/or damping device that is used tocontrol stiffness and/or damping, or combinations thereof.

In one embodiment, multiple active areas employed for actuation arewired in groups to provide graduated electrical control of force and/ordeflection output from a rolled electroactive polymer device. Forexample, a rolled electroactive polymer transducer many have 50 activeareas in which 20 active areas are coupled to one common electrode, 10active areas to a second common electrode, another 10 active areas to athird common electrode, 5 active areas to a fourth common electrode inthe remaining five individually wired. Suitable computer management andon-off control for each common electrode then allows graduated force anddeflection control for the rolled transducer using only binary on/offswitching. The biological analogy of this system is motor units found inmany mammalian muscular control systems. Obviously, any number of activeareas and common electrodes may be implemented in this manner to providea suitable mechanical output or graduated control system.

Multiple Degree of Freedom Devices

In another embodiment, multiple active areas on an electroactive polymerare disposed such subsets of the active areas radially align afterrolling. For example, the multiple the active areas may be disposed suchthat, after rolling, active areas are disposed every 90 degrees in theroll. These radially aligned electrodes may then be actuated in unity toallow multiple degree of freedom motion for a rolled electroactivepolymer device. Similarly, multiple degrees of freedom may be obtainedfor unrolled electroactive polymer devices, such as those described withrespect to FIGS. 4F and 4G. Thus, the rolled polymer devices are oneembodiment of multi degrees of freedom that may be obtained withtransducer configuration of the present invention.

FIG. 4L illustrates a rolled transducer 180 capable of two-dimensionaloutput in accordance with one environment of the present invention.Transducer 180 comprises an electroactive polymer 182 rolled to provideten layers. Each layer comprises four radially aligned active areas. Thecenter of each active area is disposed at a 90 degree increment relativeto its neighbor. FIG. 4L shows the outermost layer of polymer 182 andradially aligned active areas 184, 186, and 188, which are disposed suchthat their centers mark 90 degree increments relative to each other. Afourth radially aligned active area (not shown) on the backside ofpolymer 182 has a center approximately situated 180 degrees fromradially aligned active area 186.

Radially aligned active area 184 may include common electricalcommunication with active areas on inner polymer layers having the sameradial alignment. Likewise, the other three radially aligned outeractive areas 182, 186, and the back active area not shown, may includecommon electrical communication with their inner layer counterparts. Inone embodiment, transducer 180 comprises four leads that provide commonactuation for each of the four radially aligned active area sets.

FIG. 4M illustrates transducer 180 with radially aligned active area188, and its corresponding radially aligned inner layer active areas,actuated. Actuation of active area 188, and corresponding inner layeractive areas, results in axial expansion of transducer 188 on theopposite side of polymer 182. The result is lateral bending oftransducer 180, approximately 180 degrees from the center point ofactive area 188. The effect may also be measured by the deflection of atop portion 189 of transducer 180, which traces a radial arc from theresting position shown in FIG. 4L to his position at shown in FIG. 4M.Varying the amount of electrical energy provided to active area 188, andcorresponding inner layer active areas, controls the deflection of thetop portion 189 along this arc. Thus, top portion 189 of transducer 180may have a deflection as shown in FIG. 4L, or greater, or a deflectionminimally away from the position shown in FIG. 4L. Similar bending in ananother direction may be achieved by actuating any one of the otherradially aligned active area sets.

Combining actuation of the radially aligned active area sets produces atwo-dimensional space for deflection of top portion 189. For example,radially aligned active area sets 186 and 184 may be actuatedsimultaneously to produce deflection for the top portion in a 45 degreeangle corresponding to the coordinate system shown in FIG. 4L.Decreasing the amount of electrical energy provided to radially alignedactive area set 186 and increasing the amount of electrical energyprovided to radially aligned active area set 184 moves top portion 189closer to the zero degree mark. Suitable electrical control then allowstop portion 189 to trace a path for any angle from 0 to 360 degrees, orfollow variable paths in this two dimensional space.

Transducer 180 is also capable of three-dimensional deflection.Simultaneous actuation of active areas on all four sides of transducer180 will move top portion 189 upward. In other words, transducer 180 isalso a linear actuator capable of axial deflection based on simultaneousactuation of active areas on all sides of transducer 180. Coupling thislinear actuation with the differential actuation of radially alignedactive areas and their resulting two-dimensional deflection as justdescribed above, results in a three dimensional deflection space for thetop portion of transducer 180. Thus, suitable electrical control allowstop portion 189 to move both up and down as well as tracetwo-dimensional paths along this linear axis.

Although transducer 180 is shown for simplicity with four radiallyaligned active area sets disposed at 90 degree increments, it isunderstood that transducers of the present invention capable of two- andthree-dimensional motion may comprise more complex or alternate designs.For example, eight radially aligned active area sets disposed at 45degree increments. Alternatively, three radially aligned active areasets disposed at 120 degree increments may be suitable for 2D and 3-Dmotion.

In addition, although transducer 180 is shown with only one set of axialactive areas, the structure of FIG. 4L is modular. In other words, thefour radially aligned active area sets disposed at 90 degree incrementsmay occur multiple times in an axial direction. For example, radiallyaligned active area sets that allow two- and three-dimensional motionmay be repeated ten times to provide a wave pattern that may beimpressed on a fluid flow.

Sensing

Electroactive polymers of the present invention may also be configuredas a sensor. Generally, electroactive polymer sensors of this inventiondetect a “parameter” and/or changes in the parameter. The parameter isusually a physical property of an object such as its temperature,density, strain, deformation, velocity, location, contact, acceleration,vibration, volume, pressure, mass, opacity, concentration, chemicalstate, conductivity, magnetization, dielectric constant, size, etc. Insome cases, the parameter being sensed is associated with a physical“event”. The physical event that is detected may be the attainment of aparticular value or state of a physical or chemical property.

An electroactive polymer sensor is configured such that a portion of theelectroactive polymer deflects in response to the change in a parameterbeing sensed. The electrical energy state and deflection state of thepolymer are related. The change in electrical energy or a change in theelectrical impedance of an active area resulting from the deflection maythen be detected by sensing electronics in electrical communication withthe active area electrodes. This change may comprise a capacitancechange of the polymer, a resistance change of the polymer, and/orresistance change of the electrodes, or a combination thereof.Electronic circuits in electrical communication with electrodes detectthe electrical property change. If a change in capacitance or resistanceof the transducer is being measured for example, one applies electricalenergy to electrodes included in the transducer and observes a change inthe electrical parameters.

In one embodiment, deflection is input into an active area sensor insome manner via one or more coupling mechanisms. In one embodiment, thechanging property or parameter being measured by the sensor correspondsto a changing property of the electroactive polymer, e.g. displacementor size changes in the polymer, and no coupling mechanism is used.Sensing electronics in electrical communication with the electrodesdetect change output by the active area. In some cases, a logic devicein electrical communication with sensing electronics of sensorquantifies the electrical change to provide a digital or other measureof the changing parameter being sensed. For example, the logic devicemay be a single chip computer or microprocessor that processesinformation produced by sensing electronics. Electroactive polymersensors are further described in Ser. No. 10/007,705, which isincorporated herein by reference for all purposes.

An active area may be configured such that sensing is performedsimultaneously with actuation of the active area. For a monolithictransducer, one active area may be responsible for actuation and anotherfor sensing. Alternatively, the same active area of a polymer may beresponsible for actuation and sensing. In this case, a low amplitude,high frequency AC (sensing) signal may be superimposed on the driving(actuation) signal. For example, a 1000 Hz sensing signal may besuperimposed on a 10 Hz actuation signal. The driving signal will dependon the application, or how fast the actuator is moving, but drivingsignals in the range from less than 0.1 Hz to about 1 million Hz aresuitable for many applications. In one embodiment, the sensing signal isat least about 10 times faster than the motion being measured. Sensingelectronics may then detect and measure the high frequency response ofthe polymer to allow sensor performance that does not interfere withpolymer actuation. Similarly, if impedance changes are detected andmeasured while the electroactive polymer transducer is being used as agenerator, a small, high-frequency AC signal may be superimposed on thelower-frequency generation voltage signal. Filtering techniques may thenseparate the measurement and power signals.

Active areas of the present invention may also be configured to providevariable stiffness and damping functions. In one embodiment, open looptechniques are used to control stiffness and/or damping of a deviceemploying an electroactive polymer transducer; thereby providing simpledesigns that deliver a desired stiffness and/or damping performancewithout sensor feedback. For example, control electronics in electricalcommunication with electrodes of the transducer may supply asubstantially constant charge to the electrodes. Alternately, thecontrol electronics may supply a substantially constant voltage to theelectrodes. Systems employing an electroactive polymer transducer offerseveral techniques for providing stiffness and/or damping control. Anexemplary circuit providing stiffness/damping control is provided below.

While not described in detail, it is important to note that active areasand transducers in all the figures and discussions for the presentinvention may convert between electrical energy and mechanical energybi-directionally (with suitable electronics). Thus, any of the rolledpolymers, active areas, polymer configurations, transducers, and devicesdescribed herein may be a transducer for converting mechanical energy toelectrical energy (generation, variable stiffness or damping, orsensing) and for converting electrical energy to mechanical energy(actuation, variable stiffness or damping, or sensing). Typically, agenerator or sensor active area of the present invention comprises apolymer arranged in a manner that causes a change in electric field inresponse to deflection of a portion of the polymer. The change inelectric field, along with changes in the polymer dimension in thedirection of the field, produces a change in voltage, and hence a changein electrical energy.

Often the transducer is employed within a device that comprises otherstructural and/or functional elements. For example, external mechanicalenergy may be input into the transducer in some manner via one or moremechanical transmission coupling mechanisms. For example, thetransmission mechanism may be designed or configured to receiveflow-generated mechanical energy and to transfer a portion of theflow-generated mechanical energy to a portion of a polymer where thetransferred portion of the flow generated mechanical energy results in adeflection in the transducer. The flow-generated mechanical energy mayproduce an inertial force or a direct force where a portion of theinertial force or a portion of the direct force is received by thetransmission mechanism.

Conditioning Electronics

Devices of the present invention may also rely on conditioningelectronics that provide or receive electrical energy from electrodes ofan active area for one of the electroactive polymer functions mentionedabove. Conditioning electronics in electrical communication with one ormore active areas may include functions such as stiffness control,energy dissipation, electrical energy generation, polymer actuation,polymer deflection sensing, control logic, etc.

For actuation, electronic drivers may be connected to the electrodes.The voltage provided to electrodes of an active area will depend uponspecifics of an application. In one embodiment, an active area of thepresent invention is driven electrically by modulating an appliedvoltage about a DC bias voltage. Modulation about a bias voltage allowsfor improved sensitivity and linearity of the transducer to the appliedvoltage. For example, a transducer used in an audio application may bedriven by a signal of up to 200 to 100 volts peak to peak on top of abias voltage ranging from about 750 to 2000 volts DC.

Suitable actuation voltages for electroactive polymers, or portionsthereof, may vary based on the material properties of the electroactivepolymer, such as the dielectric constant, as well as the dimensions ofthe polymer, such as the thickness of the polymer film For example,actuation electric fields used to actuate polymer 12 in FIG. 2A mayrange in magnitude from about 0 V/m to about 440 MV/m. Actuationelectric fields in this range may produce a pressure in the range ofabout 0 Pa to about 10 MPa. In order for the transducer to producegreater forces, the thickness of the polymer layer may be increased.Actuation voltages for a particular polymer may be reduced by increasingthe dielectric constant, decreasing the polymer thickness, anddecreasing the modulus of elasticity, for example.

FIG. 4N illustrates an electrical schematic of an open loop variablestiffness/damping system in accordance with one embodiment of thepresent invention. System 130 comprises an electroactive polymertransducer 132, voltage source 134, control electronics comprisingvariable stiffness/damping circuitry 136 and open loop control 138, andbuffer capacitor 140.

Voltage source 134 provides the voltage used in system 130. In thiscase, voltage source 134 sets the minimum voltage for transducer 132.Adjusting this minimum voltage, together with open loop control 138,adjusts the stiffness provided by transducer 132. Voltage source 134also supplies charge to system 130. Voltage source 134 may include acommercially available voltage supply, such as a low-voltage batterythat supplies a voltage in the range of about 1-15 Volts, and step-upcircuitry that raises the voltage of the battery. In this case, voltagestep-down performed by step-down circuitry in electrical communicationwith the electrodes of transducer 132 may be used to adjust anelectrical output voltage from transducer 132. Alternately, voltagesource 134 may include a variable step-up circuit that can produce avariable high voltage output from the battery. As will be described infurther detail below, voltage source 134 may be used to apply athreshold electric field as described below to operate the polymer in aparticular stiffness regime.

The desired stiffness or damping for system 130 is controlled byvariable stiffness/damping circuitry 136, which sets and changes anelectrical state provided by control electronics in system 130 toprovide the desired stiffness/damping applied by transducer 132. In thiscase, stiffness/damping circuitry 36 inputs a desired voltage to voltagesource 134 and/or inputs a parameter to open loop control 138.Alternately, if step-up circuitry is used to raise the voltage source134, circuitry 136 may input a signal to the step-up circuitry to permitvoltage control.

As transducer 132 deflects, its changing voltage causes charge to movebetween transducer 132 and buffer capacitor 140. Thus, externallyinduced expansion and contraction of transducer 132, e.g., from avibrating mechanical interface, causes charge to flow back and forthbetween transducer 132 and buffer capacitor 140 through open loopcontrol 138. The rate and amount of charge moved to or from transducer132 depends on the properties of buffer capacitor 140, the voltageapplied to transducer 132, any additional electrical components in theelectrical circuit (such as a resistor used as open loop control 138 toprovide damping functionality as current passes there through), themechanical configuration of transducer 132, and the forces applied to orby transducer 132. In one embodiment, buffer capacitor 140 has a voltagesubstantially equal to that of transducer 132 for zero displacement oftransducer 132, the voltage of system 130 is set by voltage source 134,and open loop control 138 is a wire; resulting in substantially freeflow of charge between transducer 132 and buffer capacitor 140 fordeflection of transducer 132.

Open loop control 138 provides a passive (no external energy supplied)dynamic response for stiffness applied by transducer 132. Namely, thestiffness provided by transducer 132 may be set by the electricalcomponents included in system 130, such as the control electronics andvoltage source 134, or by a signal from control circuitry 136 actingupon one of the electrical components. Either way, the response oftransducer 132 is passive to the external mechanical deflections imposedon it. In one embodiment, open loop control 138 is a resistor. One canalso set the resistance of the resistor to provide an RC time constantrelative to a time of interest, e.g., a period of oscillation in themechanical system that the transducer is implemented in. In oneembodiment, the resistor has a high resistance such that the RC timeconstant of open loop control 138 and transducer 132 connected in seriesis long compared to a frequency of interest. In this case, thetransducer 132 has a substantially constant charge during the time ofinterest. A resistance that produces an RC time constant for theresistor and the transducer in the range of about 5 to about 30 timesthe period of a frequency of interest may be suitable for someapplications. For applications including cyclic motion, increasing theRC time constant much greater than the mechanical periods of interestallows the amount of charge on electrodes of transducer 132 to remainsubstantially constant during one cycle. In cases where the transduceris used for damping, a resistance that produces an RC time constant forthe resistor and the transducer in the range of about 0.1 to about 4times the period of a frequency of interest may be suitable. As one ofskill in the art will appreciate, resistances used for the resistor mayvary based on application, particularly with respect to the frequency ofinterest and the size (and therefore capacitance C) of the transducer132.

In one embodiment of a suitable electrical state used to controlstiffness and/or damping using open loop techniques, the controlelectronics apply a substantially constant charge to electrodes oftransducer 132, aside from any electrical imperfections or circuitdetails that minimally affect current flow. The substantially constantcharge results in an increased stiffness for the polymer that resistsdeflection of transducer 132. One electrical configuration suitable forachieving substantially constant charge is one that has a high RC timeconstant, as described. When the value of the RC time constant of openloop control 138 and transducer 132 is long compared to the frequency ofinterest, the charge on the electrodes for transducer 132 issubstantially constant. Further description of stiffness and/or dampingcontrol is further described in commonly owned U.S. Pat. No. 6,882,086,which is described herein for all purposes.

For generation, mechanical energy may be applied to the polymer oractive area in a manner that allows electrical energy changes to beremoved from electrodes in contact with the polymer. Many methods forapplying mechanical energy and removing an electrical energy change fromthe active area are possible. Rolled devices may be designed thatutilize one or more of these methods to receive an electrical energychange. For generation and sensing, the generation and utilization ofelectrical energy may require conditioning electronics of some type. Forinstance, at the very least, a minimum amount of circuitry is needed toremove electrical energy from the active area. Further, as anotherexample, circuitry of varying degrees of complexity may be used toincrease the efficiency or quantity of electrical generation in aparticular active area or to convert an output voltage to a more usefulvalue.

FIG. 5A is block diagram of one or more active areas 600 on a transducerthat connected to power conditioning electronics 610. Potentialfunctions that may be performed by the power conditioning electronics610 include but are not limited to 1) voltage step-up performed bystep-up circuitry 602, which may be used when applying a voltage toactive areas 600, 2) charge control performed by the charge controlcircuitry 604 which may be used to add or to remove charge from theactive areas 600 at certain times, 3) voltage step-down performed by thestep-down circuitry 608 which may be used to adjust an electrical outputvoltage to a transducer. All of these functions may not be required inthe conditioning electronics 610. For instance, some transducer devicesmay not use step-up circuitry 602, other transducer devices may not usestep-down circuitry 608, or some transducer devices may not use step-upcircuitry and step-down circuitry. Also, some of the circuit functionsmay be integrated. For instance, one integrated circuit may perform thefunctions of both the step-up circuitry 602 and the charge controlcircuitry 608.

FIG. 5B is a circuit schematic of an rolled device 603 employing atransducer 600 for one embodiment of the present invention. As describedabove, transducers of the present invention may behave electrically asvariable capacitors. To understand the operation of the transducer 603,operational parameters of the rolled transducer 603 at two times, t₁ andt₂ may be compared. Without wishing to be constrained by any particulartheory, a number of theoretical relationships regarding the electricalperformance the generator 603 are developed. These relationships are notmeant in any manner to limit the manner in which the described devicesare operated and are provided for illustrative purposes only.

At a first time, t₁, rolled transducer 600 may possess a capacitance,C₁, and the voltage across the transducer 600 may be voltage 601, V_(B).The voltage 601, V_(B), may be provided by the step-up circuitry 602. Ata second time t₂, later than time t₁, the transducer 600 may posses acapacitance C₂ which is lower than the capacitance C₁. Generallyspeaking, the higher capacitance C1 occurs when the polymer transducer600 is stretched in area, and the lower capacitance C2 occurs when thepolymer transducer 600 is contracted or relaxed in area. Without wishingto bound by a particular theory, the change in capacitance of a polymerfilm with electrodes may be estimated by well known formulas relatingthe capacitance to the film's area, thickness, and dielectric constant.

The decrease in capacitance of the transducer 600 between t₁ and t₂ willincrease the voltage across the transducer 600. The increased voltagemay be used to drive current through diode 616. The diode 615 may beused to prevent charge from flowing back into the step-up circuitry atsuch time. The two diodes, 615 and 616, function as charge controlcircuitry 604 for transducer 600 which is part of the power conditioningelectronics 610 (see FIG. 5A). More complex charge control circuits maybe developed depending on the configuration of the generator 603 and theone or more transducers 600 and are not limited to the design in FIG.5B.

A transducer may also be used as an electroactive polymer sensor tomeasure a change in a parameter of an object being sensed. Typically,the parameter change induces deflection in the transducer, which isconverted to an electrical change output by electrodes attached to thetransducer. Many methods for applying mechanical or electrical energy todeflect the polymer are possible. Typically, the sensing of electricalenergy from a transducer uses electronics of some type. For instance, aminimum amount of circuitry is needed to detect a change in theelectrical state across the electrodes.

FIG. 6 is a schematic of a sensor 450 employing a transducer 451according to one embodiment of the present invention. As shown in FIG.7, sensor 450 comprises transducer 451 and various electronics 455 inelectrical communication with the electrodes included in the transducer451. Electronics 455 are designed or configured to add, remove, and/ordetect electrical energy from transducer 451. While many of the elementsof electronics 455 are described as discrete units, it is understoodthat some of the circuit functions may be integrated. For instance, oneintegrated circuit may perform the functions of both the logic device465 and the charge control circuitry 457.

In one embodiment, the transducer 451 is prepared for sensing byinitially applying a voltage between its electrodes. In this case, avoltage, V_(I), is provided by the voltage 452. Generally, V_(I) is lessthan the voltage required to actuate transducer 451. In someembodiments, a low-voltage battery may supply voltage, V_(I), in therange of about 1-15 Volts. In any particular embodiment, choice of thevoltage, V_(I) may depend on a number of factors such as the polymerdielectric constant, the size of the polymer, the polymer thickness,environmental noise and electromagnetic interference, compatibility withelectronic circuits that might use or process the sensor information,etc. The initial charge is placed on transducer 451 using electronicscontrol sub-circuit 457. The electronics control sub-circuit 457 maytypically include a logic device such as single chip computer ormicrocontroller to perform voltage and/or charge control functions ontransducer 451. The electronics control sub-circuit 457 is thenresponsible for altering the voltage provided by voltage 452 toinitially apply the relatively low voltage on transducer 451.

Sensing electronics 460 are in electrical communication with theelectrodes of transducer 451 and detect the change in electrical energyor characteristics of transducer 451. In addition to detection, sensingelectronics 460 may include circuits configured to detect, measure,process, propagate, and/or record the change in electrical energy orcharacteristics of transducer 451. Electroactive polymer transducers ofthe present invention may behave electrically in several ways inresponse to deflection of the electroactive polymer transducer.Correspondingly, numerous simple electrical measurement circuits andsystems may be implemented within sensing electronics 460 to detect achange in electrical energy of transducer 451. For example, iftransducer 451 operates in capacitance mode, then a simple capacitancebridge may be used to detect changes in transducer 451 capacitance. Inanother embodiment, a high resistance resistor is disposed in serieswith transducer 451 and the voltage drop across the high resistanceresistor is measured as the transducer 451 deflects. More specifically,changes in transducer 451 voltage induced by deflection of theelectroactive polymer are used to drive current across the highresistance resistor. The polarity of the voltage change across resistorthen determines the direction of current flow and whether the polymer isexpanding or contracting. Resistance sensing techniques may also be usedto measure changes in resistance of the polymer included or changes inresistance of the electrodes. Some examples of these techniques aredescribed in commonly owned U.S. Pat. No. 6,809,462, which waspreviously incorporated by reference.

CONCLUSION

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations, and equivalents thatfall within the scope of this invention which have been omitted forbrevity's sake. For example, although the present invention has beendescribed in terms of several specific electrode materials, the presentinvention is not limited to these materials and in some cases mayinclude air as an electrode. In addition, although the present inventionhas been described in terms of circular rolled geometries, the presentinvention is not limited to these geometries and may include rolleddevices with square, rectangular, or oval cross sections and profiles.It is therefore intended that the scope of the invention should bedetermined with reference to the appended claims.

1. A device for affecting fluid flow, the device comprising: anelectroactive polymer transducer comprising at least two compliantelectrodes and an electroactive polymer in electrical communication withthe at least two compliant electrodes, wherein a portion of theelectroactive polymer is arranged to deflect from a first position to asecond position in response to a change in electric field applied to theat least two compliant electrodes; at least one surface of the device incontact with a fluid and operatively coupled to the electroactivepolymer transducer, wherein the deflection of the portion of theelectroactive polymer causes a change in a characteristic of the fluidthat is transmitted to the fluid via the one surface.
 2. The device ofclaim 1, wherein the characteristic of the fluid is selected from thegroup consisting of 1) a flow rate, 2) a flow direction, 3) a flowvorticity, 4) a flow momentum, 5) mixing, 6) flow turbulence, 7) fluidenergy, 8) a fluid thermodynamic property, 9) a fluid rheologicalproperty.